Biochemist Sylvia Tara talks about her book The Secret Life of Fat: The Science behind the Body's Least-Understood Organ and What It Means for You.

Steve Mirsky:              Science Talk will begin after this short message. 

Brian:                         Hey, there. I'm Brian.

Andrea:                       I'm Andrea. We're with Cold Spring Harbor Laboratory.

Brian:                         You've probably heard about Crisper.

Jennifer Doudna:                     So, I think this is something that everyone now is grappling with is how do we proceed. There are no easy answers.

Andrea:                       That's Jennifer Doudna, co-discoverer of the CRISPR Gene Editing Tool, talking with us on our Base Pairs podcast. We'll be back in a bit to discuss what she's concerned about. Stay tuned.

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Mirsky:                       Welcome to Scientific American Science Talk, posted on December 11, 2017. I'm Steve Mirsky. On this episode:

Sylvia Tara:                Yeah, don't ever underestimate your fat. Don't think it's something that you have to get rid of at all costs, that it's ugly, unsightly and, "I just want to do away with it." It's actually a very important endocrine organ. You need your fat, but you have to keep your fat healthy."

Mirsky:                       That's Sylvia Tara. She has a doctorate in biochemistry and she runs the website Science to Live By. Her first book is The Secret Life of Fat. She visited New York City a few months ago from her California home. We talked about the book at her Midtown hotel. So, as is often the case in such settings, also enjoy the authentic sirens of the various emergency vehicles of Manhattan.

                                    It's very, very hard to lose weight and then keep it off permanently. So, many people struggle with that. That's one of the things, just one of the many things that you talk about in the book.

Tara:                           That's right. So, fat isn't really just fat. People usually think of it as excess calories, something they have to get rid of altogether. But in truth, fat is actually an endocrine organ. Unless people really understand how fat works, it's really hard to control fat.

Mirsky:                       So, an endocrine organ is involved in hormones and –

Tara:                           Yes. It releases a number of hormones, fat. So, even though a fat molecule unto itself is responsible for energy and gives us energy, fat, collectively as an organ, fat cells and fat tissue functions as an endocrine organ meaning it releases a number of different hormones that our body depends on. For example, our brain size is linked to fat. Our immune system depends on fat to be small.

Mirsky:                       When you say our brain size, you mean evolutionarily, right?

Tara:                           No, I mean brain size.

Mirsky:                       You mean my brain size?

Tara:                           If you have defective fat that doesn't produce leptin, your brain size is different. Anorexia nervosa patients actually have shrunken brains. Right, so there's a number of different organs in our body that depend on fat for the hormones it produces. So, because of fat is actually so important within us, which is usually shocking to people, our body has ways of protecting fat. One of those ways is that one of the hormones fat produces is called leptin.

                                    Lectin has direct effect on our appetite and our metabolism. When we lose fat, we lose some leptin. Normally, leptin keeps our appetite fairly stable and it keeps our metabolism fairly high. With less leptin, our appetite goes through the roof and our metabolism goes low. So, in this way, fat will come back on us.

                                    We're driven to eat more. We get more efficient with energy when we lose some weight. This persists for up to six years. It's been studied for up to six years. It might even be permanent. So, unless you really understand the drive you have to eat after a diet, your lower metabolism after a diet, you're really predisposed to put it back on. But once you know fat and understand it, you can control it and you can take interventions then that help you deal with this issue of leptin and help you maintain weight loss.

Mirsky:                       Yeah, you talk in the book about how the constant feeling of not being satisfied is just eventually going to win out for almost everybody.

Tara:                           It does win out for almost every – a lot of people put it back on and I think it's because they don't realize what's happening in their body. They feel like they failed on a diet. They feel like this diet was supposed to be a magic bullet. "It works for everybody else. Look at these great pictures of people with six-pack abs that have been on this diet. This should happen for me, too."

                                    Then, they lose some weight and then they come off the diet and slowly and slowly – they might not even realize it but they're probably eating a little bit more because they have a stronger drive to eat now than they did before this diet. So, if you're not paying attention to that, the weight will come on slowly. It's very frustrating for dieters.

                                    So, once your eyes are opened to this fact that fat is actually an endocrine organ, it has hormones that is controlling our behavior in a way, you can then do something about it. One thing that you can do is habit becomes permanent. So, if you can get on a regimen that you can stay on, that you exercise every day, it becomes easier to counteract the effect of leptin and this higher drive to eat.

                                    I do talk about the self-control muscle in my book. I have a whole chapter on this, on techniques and behaviors people can adopt and exercise and the ways to exercise them that make this become habit so that you can do mind over fat. Your mind is now in control of your weight, of what you're going to eat. You're not driven by fat's signals to our brain, if you will, the way it talks to our brain and tells us what to do.

                                    One research piece I'll bring up is that they actually had successful dieters, people who lost 30 pounds and kept it off for 30 – sorry – 3 years or more. So, they lost 30 pounds and kept if off for 3 years. They did FMRI image analysis on their brains. They compared it to people who hadn't lost weight. They were either normal weight and never went on a diet or they were obese and weren't successful dieters at all.

                                    What they find, when these successful dieters hold a lemon lollypop in their mouth is that their reward center lights up very brightly. So, they're more excited by food. Again, it's their lower leptin probably because they're dieting. They have a more responsiveness to food. At the same time, their inhibitory centers, those centers in the brain involved with restraint also light up very brightly. So, they're able to have control over the organ. Their self-control, right, their will supersedes that excitement over food. So, both things are lighting up at the same time.

                                    This is not happening to people who are normal weight or obese people, people who are not dieting successfully. So, a really important thing is that to maintain it, you really have to be able to exercise. You have to build that part of your brain the way that successful dieters have that you can supersede any urge that there is to eat again, after the deficiency of leptin is making us hungrier.

Mirsky:                       So, that's why you call it a muscle because you can actually train it.

Tara:                           You know, it's funny. The brain acts just like a muscle. First of all, you have to train it. The other thing is that it gets fatigued. You have to give it a rest every once in a while. If you don't, you'll start coming off your diet, surprisingly enough.

                                    They find that health care workers, during the day, they're supposed to wash their hands all day. Towards the end, they don't want to wash their hands anymore. They stop. Even though there's a lot of consequences and risks to doing this, they won't do it. But when they give them longer breaks in between shifts, they'll continue to wash their hands.

                                    So, you have to find that way of respite for your brain, that you're not thinking about this. You're giving yourself some reward and it doesn't have to be food. It could be you buy something for yourself or days off, whatever it is. You find that thing that gives you some relief and some happiness that will actually help you stay on whatever regimen you pick for longer.

                                    Weight loss isn't just a six-month endeavor. It's not just a diet and we come off. It's actually a lifelong consequence. The reason for that is that once we've lost weight and our leptin is lower, our appetite is higher, our metabolism is lower. Like I said, that lasts for six years or more. So, because of that, you're permanently at a lower metabolism, possibly permanently.

                                    So, you have to maintain a diet for much longer than the six months or whatever it is that you lost weight. You now have to maintain on that 22 percent or so fewer calories than someone who hasn't lost weight to get to that. So, someone who's 170 pounds and lost weight to get to 150 pounds will have to eat 22 percent fewer calories than someone who's at 150 pounds naturally without dieting. There's a caloric penalty for losing weight. So, make sure you find a diet you can stay on for the long run and that you've got the mental tools to stay on that regimen for the long run as well.

Mirsky:                       Now the book is not just about diet tips, obviously. It's not how to lose weight. It's about what fat is. But you have a lot of personal experience in this area and it's kind of why you became a fat expert.

Tara:                           That's right. So, I struggle with fat my whole life. I mean even as a child, I would gain weight easier than other people and I would go on diets but I would not lose as much as weight as other people. Sometimes I could even gain weight on a diet. I was about to go on yet another diet. I got so tired about that. "I'm not doing this again until I understand everything there is to know about my fat. My fat is stubborn. It's not like other people's fat. I have a harder time dealing with it. I gain it easier."

Mirsky:                       This is not just a psychological impression of your difficulty. This is actual biology at work that is, indeed, truly making it more difficult for you.

Tara:                           It's true. We have different ways we get fat and we can talk about that as well. But my frustration with it just led me on a path. I'm a scientist by training and so I just decided I'm going to learn everything about it. I spent five years researching fat. I pulled out paper on fat, about 1,000 different articles and read through them all. I talked to dozens of leading researchers around the world about this cutting-edge research they were doing on fat.

                                    What I found out was so astounding I thought, "I have to capture this in a book. I have to let people know what fat really is." The Secret Life of Fat is that book. So, for me, it was a personal drive to understand it. I hope it helps other people because I think it's assumed that everyone is just overeating and they're being really lazy, but in truth, fat's much more complicated than that. The way it acts, the fact that it's an endocrine organ, itself, the fact that it's protecting itself in some ways and the body's protecting it, people really have to understand that as well as all the other ways that we get fat that I write about in section two of The Secret Life of Fat.

Mirsky:                       In the book, you talk about the difficulty you had losing weight compared with what another woman in your lab group there could eat and not gain any weight. But, now, that's among women. When you go between women and men, the difficulty for women in controlling weight compared to men is really profound.

Tara:                           Yeah, women and men really metabolize fat very differently. It's funny you say that because I was watching my man eat ice cream every night and yet fit into his college jeans that drove me to write that chapter, do the research and write that chapter. I found the answers I was looking for. So, women actually – from the time we're born, girls have more fat than baby boys. I think it probably happens even within the womb. We have more fat.

                                    Some of the reasons for that are that we partition more nutrients into fat than men do. So, for example, if we're eating 100 calories, women will put about 30 of those calories and divert it into fat tissue. Men might do 20, 20 or 15 say. So, we're shuttling more of the nutrients into fat.

                                    The other thing is that we interact with our fat differently. So, at a time of fat, women will actually use fat as energy more than men will. Men will reach for glycogen and protein more for energy. Women will reach for fat. You would think this was a great thing, that we can actually now use our fat. We're losing fat.

                                    But in those other times, as soon as we're passed that time of need or fast, we actually store more of our triglycerides, circulating triglycerides into fat very quickly. So, our bodies are very efficient. We use fat and we store it back in very quickly. That actually makes us fatter in a way, but healthier. We don't have those circulating triglycerides the way men do. Women tend to be a little bit more metabolically healthy than men. Some of that changes around menopause. Women start to get visceral fat and start to have some of the same issues, but overall, women's fat is protective for them.

                                    Another interesting thing is women respond to exercise a little bit differently. I write about this in The Secret Life of Fat. When women do intense exercise, say burning off 600 calories or so, we actually get elevated levels of ghrelin, which is a hormone that comes from our stomach that makes us hungry. It's a hunger hormone. It raises about 33 percent more than a man's will.

                                    Even after women satiate themselves, after they eat, they will still have a 25 percent higher level of ghrelin. So, they tend to overcompensate after exercise. So, nature really has designed women in a way to have a little bit more body fat. I'm sure there's evolutionary advantages for that. We do give birth. During lactation, we use our fat for energy. So, a lot of reasons for that.

                                    But in any case, women should feel a little bit more, hopefully, appreciative of their fat. It is keeping them healthy. Probably, I know, a little bit healthier than some of the male counterparts in their lives. Gender is only reason that some people have more fat than others. There's also – our microbiome has a factor in how much fatness we get. Viruses are even tied to fat. Genetics has a big component of our fat. As does age. As we age, our hormone will decrease and that causes fat almost as a force of nature to start accumulating on us with age.

Mirsky:                       Yeah, this is something that I definitely noticed once I turned about 45. Pounds just seemed to appear out of nowhere. But you talk in the book about, which I didn't know, once I get to be about 70, this is probably going to reverse itself and I'll be able to – or without even trying, I'll lose weight.

Tara:                           It's not necessarily a good thing. So, as we age, fat has different roles and functions in our body, honestly. When we're babies, we have a lot of brown fat. Brown fat is a type of fat that actually produces heat. It burns energy for heat. It's a higher proportion of babies.

                                    Then, as we go through puberty, our fat's really important for reproduction. Actually, women who don't have enough fat, they usually don't get menstrual cycles or they stop. So, it's directly linked, our fat, with reproduction. Then, again, during pregnancy it's important. Middle age, we start to accumulate it. We get these kind of beer guts and we get more hips on our thighs if we're women.

                                    But then, amazingly, as we get older into the 70s and 80s, we start to lose some fat tissue. It's because our fat cells start to atrophy a little bit. They're not as strong anymore. They actually don't hold as much fat. So, you feel like you're getting thinner but really, you're getting less healthy. Because now that your fat tissue can't hold as much fat, that fat is circulating in your blood. It's going into other places it shouldn't be. It's going into your liver and your heart.

                                    So, it might feel like a big win, but appreciate your fat. I guess that's one real takeaway from the book is that your fat has a real function. It's an endocrine organ. It stores fat where it needs to be and it actually in some ways keep us healthier as long as you don't have it a lot in your gut.

Mirsky:                       We'll be right back after this.

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Brian:                         Hey, Brian and Andrea, again. Co-hosts of the Base Pairs podcast from Cold Spring Harbor Laboratory. We call it the podcast about the power of genetic information.

Andrea:                       That's why we're thrilled to share our latest episode where we talk about how American science once took a wrong turn toward eugenics. Come find us on Apple podcasts, Stitcher, Sound Cloud, Google Play or wherever else you get your podcasts.

[Music]

Mirsky:                       Now more with Sylvia Tara.

                                    You talk in the book about sumo wrestlers as an example of what we call fat but fit. So, just because you're overweight, or whatever that even means, just because you're round, let's say, does not necessarily mean that you're unhealthy.

Tara:                           That's right. We have all different kinds of fat in our body. This is something people really have to understand. So, one type of fat we have is subcutaneous fat. It's that fat that's right underneath our skin, so in our arms, in our legs, in the buttock area. There's also visceral fat. That's fat underneath the stomach wall that is nestled against your internal organs. That tends to make people unhealthy. Now other types of fat – we touched on brown fat. So, brown fat exists around our heart region, our clavicles, our spine. That is fat that actually burns energy.

                                    So, unlike white fat, it's not storing energy as much as using energy to produce heat in our bodies. Like I said, babies have quite a bit of brown fat. They have a higher proportion of it. There's also a newly discovered beige fat. That's fat that can turn brown and does turn brown upon exercise. There's a hormone called irisin that actually will turn it brown. Research on cold exposure is being looked at now as a way to increase our amounts of brown fat that will help us burn energy.

Mirsky:                       Because shivering is an unbelievable workout.

Tara:                           That's right. So, a cold swim actually will burn quite a bit of calories. So, the bad fat that people are always – what they hear about in the news, this correlation with diabetes and cardiovascular disease, they tend to be around visceral fat and that is the fat under your stomach wall. What happens is when that fat gets crowded, it starts to get inflamed, meaning it gets a lot more cytokines in it, a lot more immune cells. That interferes with insulin signaling.

                                    So, you're not responding to insulin as well. You're not internalizing glucose and fats out of your blood. They're hanging around in the blood, depositing in other areas where they shouldn't be. That correlates with the diabetes and the heart disease that people hear about. So, the most important fat to get rid of is visceral fat.

                                    Now sumo wrestlers are a very interesting case of fit but fat, because they eat about 5,000 to 7,000 calories a day. Obese by any measure, no doubt. But they exercise six to seven hours a day, actually. Now fat has another trick up its sleeve. Fat can produce another hormone called adiponectin. Now adiponectin actually helps guide circulating triglycerides out of the blood and into fat tissue, subcutaneous fat tissue where it belongs. It's the healthier store of fat tissue. It's fat's way of talking. Again, it's pretty much saying, "Hey, fat, come home. Come home to where you belong." Right? So, exercise promotes the release of adiponectin from fat.

                                    So, when sumo wrestlers exercise for six to seven hours a day, they're increasing their adiponectin levels. Adiponectin also reduces visceral fat. So, metabolically, sumo wrestlers are healthy. They don't have very high circulating triglycerides. They don't have much visceral fat at all. They don't really get diabetes and heart disease as you would expect.

                                    But interestingly, when they come off the sumo regimen and they stop exercising as much and they eat some processed foods, they come off the sumo diet, they get unhealthy very quickly. So, their exercise program is actually keeping them healthy. So, sumos are a curious case of fit but fat.

Mirsky:                       I don't want to go off on a sumo tangent, but it is fascinating. Do most of them wind up losing weight after they are competitive? Do you know?

Tara:                           No, I don't know. I know that you get unhealthy for a while. So, I'm assuming if they have some prompt – if they're working with a doctor – I don't know that they ever really lose all that weight and it's hard to do. As we talked about, once fat's on you, there's all kinds of mechanisms by which it will stay on you not only the leptin issue that when you lose it you get hungrier and your metabolism's slower, we also divert more blood supply to fat. So, fat, like cancer – cancers can do this, too. Tumors can do this, too. They are clever enough to divert blood supply to itself.

Mirsky:                       And create blood vessels.

Tara:                           Create blood vessels that will feed it –

Mirsky:                       Angiogenesis.

Tara:                           Angiogenesis, that will feed it, give it oxygen, give it nutrients to survive. So, just like tumors, fat can do this, too. It becomes another pathway by which nutrients come to fat and get deposited within fat. So, when you want to lose fat, you're really remodeling your body in a way. You're getting rid of this whole bunch of tissue that's been in existence for a long time.

                                    You're having to do away with some veins. Prune them or have them atrophy or whatever. But it actually is a pretty major endeavor to remodel your body in that way. I'm sure once sumo wrestlers have all that fat, it's pretty hard for them to lose it.

Mirsky:                       It's a fascinating study you mention in the book, just to talk about how valuable fat is, about healing. A mouse study where mice who were – well, why don't you talk about what the – more rapid healing if they had the fat available.

Tara:                           Yes. So, fat affects so many things you would never expect it affects. We talked about the brain size is linked to fat. We talked about the immune cells, T cells have receptors for leptin. So, fat affects the number of T cells that we have, subgroups of T cells that we have. But also, our veins have receptors for leptin. So, our endothelial cells. Interestingly enough, they find that when they block leptin we don't heal as quickly. So, mice, where they put lesions in them and they block leptin, it takes them two days longer to heal a wound than the ones that have normal levels of leptin.

                                    Anorexia nervosa patients, once again, they have the same problem. They're leptin deficient. Clearly, they have very, very low fat stores. They have very low T cell counts and it takes them longer to heal when they get a skin lesion. So, don't ever underestimate your fat. Don't think it's something that you have to get rid of at all costs, that it's ugly, unsightly and I just want to do away with it. It's actually a very important endocrine organ. You need your fat, but you have to keep your fat healthy.

                                    I'm not promoting obesity, but appreciate your fat. It's really working hard for you in your body. I think once you understand it, you'll be able to actually manage it better. You'll know it's a healthy level and you'll be able to lose it a little bit better where it's not supposed to be, particularly visceral fat.

Mirsky:                       I have lived through the don't eat any carbs phase of American dieting to don't eat any fat phase of American dieting. Now, I'm not sure where we are now. But it seems like maybe we're in a more balanced general attitude.

Tara:                           Yeah, there are so many diets out there. If I were to address every one of these, it would be an all-day show. But a diet has to work for you biologically. So, in my book, The Secret Life of Fat, I talk about all the ways we get fat that aren't all to do with overeating. Certainly, overeating will make you fat. But genetics will have a role in fat. I talk about the Pima Indians. There's populations more susceptible to getting fat.

Mirsky:                       Let's talk about that for a little bit. I first started seeing articles in, I think, the '80s on the propensity of some Native Americans to really just horde fat. What was it, the thrifty gene is what they referred to it as.

Tara:                           Yeah, thrifty genotype, that's right. So, I talk about or I write about the Pima Indians in my book a little bit. It's a great example of how our genes interact with the environment and how that affects different populations differently. So, the Pima Indians crossed over the Bering Strait around 30,000 years ago. They settled in different regions. One group settled in Phoenix, Arizona area. Another group went down to Mayakoba, Mexico.

                                    The Pimas, they hunted, they farmed. They had pretty active lives. They did experience droughts and famine several times a century. Geneticists believe they evolved a thrifty genotype which is a collection of genes that helped them become very efficient with their energy and it also helped them store fat very quickly and very easily. It served them really well, right, for centuries.

                                    Now the Phoenix Pima started diverging a bit from Mayakoba Pima in that they started encountering Caucasians, westerners coming in from the gold rush in the 1800s. They started eating more Western foods. At some point, their land got limited and they didn't do hunting and farming as much anymore. The U.S. Government actually intervened and started giving them food assistance. So, they got canned meat. They got flour. They got lard. They got other staples as well, but very much looking like an American diet.

Mirsky:                       And they got fat.

Tara:                           They got really fat. Caucasians in the area, also having a similar lifestyle. So, both populations out there, they're not farming anymore. They're working in factories. They're working in military. They're doing other things, and they're eating a Western diet.

                                    But the Pima Indians got three times higher obesity rates than those – than the Caucasians nearby largely living the same lifestyle. When they compared it to the Macoba Indians in Mexico, they had ten times higher obesity rate. Because the Macoba in Mexico actually stayed with the rural lifestyles. They were still hunting and farming. They didn't even have cars. They were riding bikes.

                                    So, that thrifty genotype that made the Pima so successful at surviving drought and famine was now really hurting them. Their bodies were waiting for a famine that was never coming anymore. They were in the land of plenty now. So, it's really – it's a good illustration of how our genes really matter. So, what our ancestry is, what lineage we come from, and how that affects the current life – the lives that we live now and what that means to our body, it's a good example. There's other populations, too. There's ______ in the Pacific is another example of a population that's gotten fat.

                                    Then more specifically, there are genes specifically identified linked to fat. There's the FTO variant which even Caucasians now are talking about. They have a higher propensity to eat high-energy dense foods. Naturally, they have more weight. But that gene also creates more white fat cells. There's the IRS1 gene's another one that I write about in The Secret Life of Fat.

                                    So, there's much more research to do, but we're starting to see how our genetics plays a real role in fat. Again, it doesn't mean that you have to be obese. It means you have to take great care, more than maybe people around you. So, more than someone of a different race or lineage would have to do to manage your fat.

Mirsky:                       When modern humans evolved, just a few tens of thousands of years ago, 100,000, the environment really forced us to have a particular genome that now bites us in the backside. Here we are with this genetic legacy that we're wandering around in an environment that it doesn't work in anymore.

Tara:                           Right. It just means we need more care, we need more effort. This is where, I guess, my book differs a little bit from other books out there is that there's so many books, if you look in the bookstores, telling you it's easy. "It's easy to lose weight. You just follow my very simple plan. You just eat these certain foods. Weight will melt right off of you." It makes for the great selling of diet books.

                                    There's a lot of diet plans out there. There's a lot of different supplements people will sell you, that it's supposed to be easy. But I really face facts. I think this is the scientist in me. I face facts. I look at this and this is not so easy, especially if you have a certain predisposition, a certain genetic profile.

                                    If you have two X chromosomes it's not easy. If you have a certain microbiome, anything. If you're aging. Our hormones decline as we age, our fat-busting hormones like growth hormone and testosterone. It's going to become harder.

                                    I think you just need to look it in the eye and say, "Okay, I'm not like my 25-year-old male neighbor. I'm very different. The diet that he's on that gives him six-pack abs is not going to be something that works for me. I have to take extra measures." Don't be afraid of that hard work. It might seem very hard when you're first doing it and you think it's unfair because other people can eat, but over time, if you develop the habits around it, it starts to become second nature.

                                    I can give my own personal example. I have very, very stubborn fat. That's why I wrote the book, as I described. After all this research, I really felt empowered. None of this was depressing to me. So, this idea that we have to eat less after we lose weight because we have lower leptin and lower metabolism, I actually found that quite empowering because, for the first time, it explained why I have to eat less than other people to lose weight. I'm not gullible anymore. I don't go chasing a magic diet that might work for me. I'm very educated about fat.

Mirsky:                       You don't blame yourself for a lack of willpower when you're up against this physiological situation.

Tara:                           That's exactly right. I don't blame myself and I don't have this attitude that, "Well, I'm meant to be fat. I'm just a fat body type." I get it now. I've got a genotype probably working against me. I'm Eastern Indian. There was famine in India. I'm sure I'm not too unlike the Pima Indians. I've got two X chromosomes. I'm middle-aged. I have a bunch of things working against me. So, it just makes me stronger.

                                    So, I know these tricks that I do – the tricks I used to use in my 20s don't really work anymore. I had to come up with new tricks that work. I do write about it in the book and at length. I take pretty extreme measures and I got stronger at it. It was hard in the beginning. I do intermittent fasting where I extend the overnight fast to about 16, 17 hours.

Mirsky:                       There's a lot of data to show that that's probably a decent thing to try to do. You don't even fast for 24 hours. You just confine your eating to let's say a seven or eight-hour window during the day.

Tara:                           That's right. It's a restricted eating window. It busts through stubborn fat like you can't believe. Nothing works as well as that. it's hard to do. Believe me. I'm hungry at night. My body got used to it after a few months. I'm not as hungry as I used to be.         

                                    So, I'm able to actually maintain this very weird diet, if you will, going into years now. For years I've been doing this type of thing. There's also exercises that will help you lose weight and bust through fat. So, I think what the solution is we really look intelligently at fat, what's going on, what's going on with the hormones, what's going on with the microbiome and we develop diets around that.

                                    I kind of did it for myself after learning all this. Intermittent fasting is one thing I use. Also, a lot of high-intensity interval training. That also helped me release some hormones. I managed to lose 30 pounds and keep it off for years.

                                    We've come to a point where we really hate fat. We just want it off us at all times. In fact, in The Secret Life of Fat, I have a chapter on the history of fat, of how we've come to this point. There was actually a time in America where fat was loved after the Civil War. Food was hard to come by. There was poverty. Fat was a status symbol. There was a fat men's club that opened in 1866 where men had to be fat enough to join this very prestigious club because it was a sign of wealth.

Mirsky:                       But by 1903, they were out of business.

Tara:                           That's right. When there was industrialization, food became plentiful. Everyone could have fat. Then, people started getting scared of fat. There was these warnings about fat that to work in a factory, to work in the industrial age you had to be agile. To be in the military, you had to be strong. People started getting scared about their fat.

                                    That's when they started dieting and very weird diets came out. The tapeworm diet that was supposed to – you'd swallow tapeworms, it would siphon off your energy. Later, you would eat poison to kill the tapeworm when you were done with your diet. Fat the off soap that was supposed to dissolve the fat under your skin.

Mirsky:                       Fat off soap. You just wash yourself with this and the fat will disappear.

Tara:                           People bought this up. So, it got to the point of real, I guess, hysteria, just fear about fat, to the point that we now have multibillion-dollar corporations all fighting fat. But we're spending $60 billion a year fighting fat and yet we're fatter than ever. So, clearly, we're not scientifically understanding fat. We're not too different than the diets of before of throwing these really weird things at fat and hoping it's working.

Mirsky:                       What's the stand in your book, the $60 billion fat and $45 billion approximately for homeland security?

Tara:                           That's right. The net budget for homeland security is around $47 billion. But we spend more fighting fat than the War on Terror.

Mirsky:                       But maybe that's right because more people probably die from the fat than from the terror.

Tara:                           But the problem is we're missing our target, right?

Mirsky:                       Right, right.

Tara:                           So, we need better weapons, smarter weapons, if you will, that's really going target fats. But you have to understand what fat is. You have to retool your war strategy, I suppose.  You can only do that if you truly understand what fat is, how it's working, how clever it is, all the different, odd ways we get fat that we're not taking into consideration now. So, we be openminded about your fat. Be open to learning new things about it. Get off _____ myths about fat.

                                    It's not just calorie in and calorie out. It's a very sophisticated organ. The more you understand that, the more you'll be able to understand diets that might or might not work for you, understand why you're hungry, understand why you're getting heavier than someone else on the same diet. Just have awareness and drop the guilt. Invest in the knowledge to tool yourself to fight this the right way. Get empowered.

Mirsky:                       And for any – I'm sure a lot of people of listening are either on a diet right now or have been recently or will be soon. So, a key thing is if you go off the diet, just go back onto it the next day. I know a lot of people when they go off the diet, that's it. It's busted. They just leave it completely and then they have to start all over again in a few weeks or a month or two. So, the thing to do really is just say, "Okay, yesterday I didn't but I'm getting right back onto it today."

Tara:                           I'm really glad you brought that up. There's something called dichotomous thinking and it's a real problem for dieters. It's more common in women than it is in men. Dichotomous thinking is where you feel like a failure if you didn't reach your goal. So, it's like if I didn't get an A grade in this class, if I got anything but an A, I'm a failure. That's leads to really self-sabotaging behaviors. It's like, "Well, I'm failure so I might as well drink. I might as well eat or whatever."

                                    In dieting, personal trainers I interview see this in reality. So, when women make a mistake, it leads to another mistake. It's a self-sabotage. "I've come off my diet. So, I might as well eat this other thing now. Well, I came off it yesterday, I might as well eat this ice cream today." It becomes a slippery slope. Really, successful dieters, they just get back on.

                                    Men are better at this. They'll say, "I had a beer. Big deal, I had a beer. I'm going to get back on." They don't have this guilt. But it might happen in both genders as well. But the most important lesson in that is just get back on. Don't self-sabotage. This is not an A or a B. This is not binary.

                                    We all go off our diets and perhaps we even should once in a while. Because remember, that self-control muscle needs a break every now and then. Right? So, forgive yourself. Get back on. Just keep going.

                                    In fact, one person I interview in the book is Michael Dansinger at Tufts University. I interviewed some of his patients. They said the real strength of that program is, first, he sees them very often. He stays with them very closely. He coaches them back on the diet when they come off.

                                    He says that nobody's really 100 percent on the diet ever. People are mostly like 80, 90 percent. But to be good and have it be successful, you've got to be at about 80 or 90 percent on a diet or else they're doing 70 percent of the work and getting no benefit. So, he allows transgressions on a diet. But right after that, he'll coach people back on.

                                    Some of his patients say, "Well, he really helped me because he told me I could have ice cream, but as long as I get back on and stay on it for a number of days afterward, it's not the end of the world." Those people lose weight and they keep it off. So, be very careful about this dichotomous thinking, about this slippery slope.

                                    Allow yourself to go off once in a while, but just get back on the next day. It's not the end. It is a lifestyle. It's a life maintenance. This is not just a six-month short run. You have to live with this forever. Every now and then, you'll want to come off.

Mirsky:                       When we first met, you mentioned that visiting New York, one of the things that you're really looking forward to is a slice of New York pizza.

Tara:                           That's right.

Mirsky:                       You have to remember that eating is one of the joys of life, especially eating with friends. Just meals are such an important part of our social experience. Pizza is one of those joys among the joys. So, have a slice of pizza. Just don't have three.

Tara:                           Yeah, and don't have it too often.

Mirsky:                       Right.

Tara:                           Right. No, I couldn't agree more. I say in my book; a diet has to work biologically for _____. It has to work for you psychologically as well. If there's foods you really need to have, you've got to find a diet that allows that and it has to work for your lifestyle.

                                    So, if you're really busy, there's some diets that entail so much meal prep. There's all the different foods you need, a bunch of different foods you can't have. You have to five to seven meals a day. It doesn't work for everybody. You won't be able to stay on for the long run if you're not on a diet that works on all three dimensions; biological, psychological, and social.

                                    I couldn't agree with you more. Pizza's one of my favorite things to eat. I do eat it once in a while. But I also won't eat later the day. I'll do an intermittent fast, nonetheless. So, my behaviors are intact. I'm able to reproduce it every day without too much difficulty anymore.

                                    But I like a little more breadth in what I'm allowed to eat. For me, too, sugar is a joy of life and there's so many diet books out there now that say sugar is terrible. I agree. But I like a little bit of sweet every now and then. I'm even willing to have an extra few pounds for that little bit of sweet and joy of life. For me, psychologically, that's important.

                                    So, I opt for a diet that allows some of that and not as rigid as some other diets out there. So, find a diet that's right for you. All those three dimensions are important. Just understand your fat. There's other ways to diet than any of those diet books on the shelf. You can actually create your own diet. I did it for me. I think other people can too with the right knowledge about fat.

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Mirsky:                       Sylvia Tara is launching an online course related to The Secret Life of Fat starting January 2^nd. I'll be back in a moment.

Andrea:                       Hi, Brian and Andrea one last time. Before you go, we want to tell you why we're so excited about the power of genetic information. It helps us put food on our tables. It tells us about our ancient ancestors. It can even help us map the brain with DNA bar codes.

Brian:                         We cover a whole swath of subjects, anywhere the power of genetic information plays a role. So, check out Base Pairs, the official podcast of Cold Spring Harbor Laboratory. Search for Base Pairs wherever you get your podcasts to learn more.

Mirsky:                       That's it for this episode. Get your science news at our website, www.ScientificAmerican.com, where you can check out Larry Greenemeier's 2017 Gadget Guide, gift ideas for your loved ones. You're one of your loved ones. Follow us on Twitter where you'll get a tweet whenever a new item hits the website. Our Twitter name is @sciam. For Scientific American Science Talk, I'm Steve Mirsky. Thanks for clicking on us.

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Mirsky:                       Can you believe I never said, "We chewed the fat," one time?