APPETITE THAT KNOWS NO SATIETY: Saturated fat dulls our brain's response to appetite-suppressing hormones.
Image: istock/Soupstock
-
The Best Science Writing Online 2012
Showcasing more than fifty of the most provocative, original, and significant online essays from 2011, The Best Science Writing Online 2012 will change the way...
Read More »
When you've spent the weekend splurging on greasy fast foods, your bathroom scale isn't alone in reeling from the impact. Your brain does, too. New research shows just how saturated fat tricks us into eating more and elucidates the evolutionary basis for the propensity for poundage in developed nations. Our brain physiology, it seems, is glaringly out-of-date in the modern world.
Researchers have long known that the hormones leptin and insulin play key roles in appetite and food intake. In healthy people leptin, which is secreted by fat tissue, acts as a molecular measuring tape for our waistlines, quashing feelings of hunger. Insulin spikes when the pancreas gets a whiff of the blood sugar increase after a meal; once the brain detects the spike, it knows to tamp down the desire for food.
Certain foods and metabolic disorders, however, can disrupt our ability to respond appropriately to these hormonal signals. In a study published in the September issue of The Journal of Clinical Investigation, scientists report unraveling a central biochemical mechanism behind fat's effect on the mammalian brain . They found that after only three days on a diet high in saturated fat—a common ingredient in beef and cheese—the brains of rats and mice became resistant to leptin and insulin. In contrast, unsaturated fats, such as those found in olive oil, did not trigger resistance.
As a result of the hormone resistance, a meal high in saturated fat can crank up our appetite well after dessert. "Taking time off from a healthy diet to eat most fast foods may have consequences that last for some days, even after one resumes the healthy diet," says University of Cincinnati behavioral neuroscientist Stephen Benoit, who led the study. He believes the findings are likely to apply to humans, too.
Sensing leptin and insulin is like keeping an eye on the body's nutrient status, says Gary Schwartz, a neuroscientist at the Albert Einstein College of Medicine in New York City, who was not involved in the research. "If that eye starts to go blind because you keep giving it too much nutrient, then it can't respond. It can't tell you, 'look, don't eat.'" The result can spark a vicious cycle of metabolic problems and weight gain, he remarks.
But if the hormones are supposed to keep our metabolism from spinning out of control, why would saturated fat—the very thing that obese people have too much of—make us insensitive to them?
"There is a basic mystery here," says William Banks of the Saint Louis Veterans Affairs Medical Center. A leptin expert, he has shown that high levels of saturated fat in the bloodstream block the hormone's passage into the brain, further blinding it to those extra pounds below the neck.
One hint at an explanation for these counterintuitive effects comes from the physiology of starvation. When we starve, our body begins to break down its blubber for energy. As a result, the blood gets flooded with fat, just as it does in obesity and overeating. Apparently erring on the side of caution, our brain interprets free fat (no matter its source) as a starvation alert—had it done otherwise in our evolutionary history, we probably wouldn't be around to worry about it. Says Banks: "In the history of evolution, we've been faced with caloric shortages and starvation much more than we've ever been faced with a wealth of calories."
See what we're tweeting about
14 Comments
Add CommentSo let's keep making McDonalds, KFC, Coca-Cola and the rest pig-rich and kid-corrupting, and then we've solved some of the population problem. Go, America!
Reply | Report Abuse | Link to thisSo i buy ice-cream made with olive oil?....what's an american boy to do? Fat helps satiate the appetite while fat-free diets can also keep a person hungry. Obviously, quantity is the deciding factor. One Big Mac will cross that line Big Time.
Reply | Report Abuse | Link to thisSpiking your blood sugar with high-glycemic foods produces the same result by a different mechanism: you crave more highly-processed starchy foods & your body becomes resistant to it's own unsulin. As more studies look at the same issue from different angles, it should become even more clear that healthy living is a choice. Starchy, fatty foods are addicting. It's no wonder diabetes & heart disease are so closely linked & are on the rise. We need to take control of our own health!
Reply | Report Abuse | Link to thisThis makes a lot of sense. It explains quite a few things. If you've ever read the China Study, then you know that previous research has been done that has shown a correlation between eating large amounts of animal products and obesity as well as diabetes. To me this suggests that it's this cycle that is the main problem, not the person's self-control or even their genes.
Reply | Report Abuse | Link to thisSuggesting that saturated fats can cause obesity and diabetes is one thing. But when you consider the fact that these saturated fats are mainly obtained through eating meat, you begin to understand why there are so few obese vegetarians.
Certainly this deserves much more research, but I think it would be safe to say that this proves that the majority of us would benefit greatly from reducing our consumption of animal products. It's just too bad that it tastes soooo good.
It is not realistic or healthy to be fat-free, but rather, the quality & types of fat is the important factor. The Mediterranean diet contains higher levels of fat intake than the typical western diet. A 2 year study published in the Oct 2004 issue of JAMA found: those on the Mediterranean
Reply | Report Abuse | Link to thisdiet had a significant decrease in body weight, decreased waist circumference, decreased blood pressure, decreased fasting blood sugar, increased HDL (good cholesterol) & decreased triglyceride level. Knowledge is potential power - we can learn it, but we also need to be willing to make the change! Sadly, it is often when we personally have a life-threatening wake-up call that we become committed to doing so.
It is not realistic or healthy to be fat-free, but rather, the quality & types of fat is the important factor. The Mediterranean diet contains higher levels of fat intake than the typical western diet. A 2 year study published in the Oct 2004 issue of JAMA found: those on the Mediterranean
Reply | Report Abuse | Link to thisdiet had a significant decrease in body weight, decreased waist circumference, decreased blood pressure, decreased fasting blood sugar, increased HDL (good cholesterol) & decreased triglyceride level. Knowledge is potential power - we can learn it, but we also need to be willing to make the change! Sadly, it is often when we personally have a life-threatening wake-up call that we become committed to doing so.
I'm with you - the China Study was a good book. We could certainly do without the high levels of antibiotics given to livestock as well - they interfere with our body's ability to digect. The only part of the book I thought was lacking was the content on nutritional supplementation, which he did not thoroughly research, but merely gave his opinion, which is a bit dated. For such a landmark book, which many people refer to for health info, I was disappointed. Perhaps his son & grandchildren will revise this position in future publications, with the overwhelming body of research indicating it is prudent for all people to supplement their healthy diets with balanced, high-potency & high-quality supplementation, providing beneficial levels of antioxidants we can not attain from our food alone.
Reply | Report Abuse | Link to thisI think exercise is the key. If you eat more calories than you can burn, your are going to gain weight which is unhealthy. A good exercise program allows you to not have to stress over fats or carbohydrates. My diet tends to be low-carb because I am type 1 diabetic. As a diabetic, I can see the effects of various foods and activity levels through blood sugar monitoring. If I am getting a lot of exercise, I can get away with cheating on my diet. If I am inactive, any food will have consequences.
Reply | Report Abuse | Link to thisRight on! Exercise is so important - if we don't move it, we lose it! If we think of our bodies as race cars, then it is easy to see that how we fuel our bodies is vital. If we use dirty fuel, then the beneficial exercise is accompanied by more oxidative stress. We need the right proteins, the right carbs & healthy fats, along with optimal supplementation, providing enough antioxidants to handle free radicals produced by physical activity. Carbohydrates provide the energy we need when exercising, but we need to ensure our meal or snack is low glycemic so we do not spike our blood sugar & our energy is more stable & lasts longer.
Reply | Report Abuse | Link to thisEven olive oil, especially if heat-damaged from the cooking process, can cause an oil slick on our cell membranes; we cannot blame our " obsolete physiology" for our obesity pandemic; it's the other way round: we are ignoring plain chemical & physical laws by ingesting condensed, denatured food extracts !
Reply | Report Abuse | Link to thisIt's not a case of our "obsolete brain physiology" but our "Frankenstein" feeding habits that have led us into this pandemic of obesity! The Big Brotherhood of Fast Food Corporations is liable for this new industrial disease, caused by an inner oilslick on our trillion cell membranes.
Reply | Report Abuse | Link to thisSunny Strobe, I love your term, "oil slick" - I'll have to use that! Great comments!
Reply | Report Abuse | Link to thisthis is an annoying article at best...wrong to start with. natural sources of fat have NOTHING to do with enhancing appetite and everything to do with supressing it and sensing satisfaction... it's not the fat in the chicken thigh you eat with the skin, it is the potato chips full of msg, sugar/carbs and salt you have with it. you cant just eat 'one chip' and it has nothing to do with fat but everything to do with carbs....same reason 100 cal packs of processed JUNK do NOTHING for anybody. if you cant grow it or kill it in your back yard then you have NO business eating it
Reply | Report Abuse | Link to thisJust in case anyone else stumbles on this article based on bad research I'd like the point out that the research linked used Palmitic Acid. A form of saturated fat formed from eating high amounts of carbohydrates and fat at the same time.
Reply | Report Abuse | Link to thisAn Epi-Paleo diet or just regular Paleo diet with plenty of saturated fat does not do the same thing.
http://jackkruse.com/brain-gut-6-epi-paleo-rx/
Read his blogs on Leptin. Also Ron Rosedale of the Rosedale Diet will also refute this silly study. They are using a saturated fat that comes from eating fat and carbohydrates together. This is not the main form of saturated fat in animal products.