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That midnight trip to the fridge might be doing double damage. Most people know by now that it's poor dietary form to eat right before bed, but the body's natural circadian rhythm and related rest cycles might also have more to do with weight gain than previously thought, according to a study published online today in the journal Obesity.

With more than a third of U.S. adults tipping the scales to obese levels, rooting out the many causes of our collective weight gain has proved to be a difficult undertaking.

"How or why a person gains weight is very complicated, but it clearly is not just calories in and calories out," Fred Turek, a co-author of the study and professor of neurobiology and physiology at Northwestern University's Weinberg College of Arts in Evanston, Ill., said in a prepared statement.

Researchers in his lab at Northwestern's Center for Sleep and Circadian Biology were interested in the observed weight gain in late-night shift workers. "Their schedules force them to eat at times that conflict with their natural body rhythms" as cued by daylight and other signals, Deanna Arble, lead study author and doctoral researcher in Turek's lab, said in a prepared statement.

To examine off-schedule eating, the research team divided lab mice into two groups: active-period eaters and rest-period eaters. The mice that were given unlimited access to high-fat food only during their normal rest periods increased in heft by 48 percent, whereas those given unlimited access to fatty food during their normal activity periods put on about 20 percent of bulk over their baseline. The next step will be to pinpoint the mechanisms behind this finding, the researchers note.

The link between the circadian rhythm and weight is not a new one. In 2007, researchers located Nocturnin, a gene that works in both the circadian clock and in controlling weight gain in fatty diets. And two studies published earlier this year in Science illuminated the relationship further, detailing the role of coenzyme NAD+ in the circadian cycle and the connections between circadian protein CLOCK and the metabolic gene SIRT1.

While many of the mechanisms remain mysterious, simply shifting snack time could help some trim down. "Better timing of meals, which would require a change in behavior, could be a critical element in slowing the ever-increasing incidence of obesity," Turek said.

Image courtesy of Wikimedia Commons/Pharos

6 Comments

1. 1. jbairddo 04:49 PM 9/3/09

   For years doctors have been telling patients that it is a case of calories in-calories out and yet most people with any common sense knew the opposite. Dietitians are still dolling out advice told to them by experts who don't want to believe that what they have been told is wrong. We probably know little about the best diets since most researchers have the own reason for a particular conclusion and lay people are no less passionate about the subject. The best advice is eat like your ancestors did a 100 years ago and heed the saying, eat like a king in the morning, share your meal with a friend for lunch and eat like a pauper at dinner (or supper for the folks out west).

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2. 2. elizllo@yahoo.com 07:34 PM 9/3/09

   Snacking at bedtime can often be related to attempts to calm the brain to induce sleep by activating serotonin.
   
   Activities that may inhibit individual ease of sleep range from:
   prolonged use of microwaves to the brain from cell phones during late evening hours; exposure of the eye to the "blue frequency" of the light spectrum from computers, televisions, or hand-held gaming devices before bedtime; for some, caffeine after 3 pm; frequent carbohydrate loading which stimulates hunger pangs and, subsequently, more frequent calls for carbohydrates; high levels of cortisol in the circulation system due to inflammation in the body and/or high stress; ADHD hyper-alert brain patterns, especially to sound at night; low levels of ambient light in the sleeping area, entering the eye and suppressing melatonin production in the brain; and digestion, during sleep, of a heavy nighttime meal.
   
   These are just some of the identified inhibitors of sleep that may induce misguided attempts to mediate the problem by ingesting snacks before bedtime.
   
   It's one more case of an attempt to treat the symptom instead of the cause.
   
   Elizabeth Lowe
   Integrative Health Specialist
   Newport News, VA
   elizllo@yahoo.com
   

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3. 3. ButWhatDoIKnow 04:38 PM 9/8/09

   If it isn't just calories in versus calories out, what is it? Are some people epiphytic like spanish moss and just absorb nutrients from the air; oh, but that would still be calories in. This article seems to point out that calories out is dependent on when the calories come in. That and many other factors such as metabolism rate obviously makes for a complicated equation. But common sense to me seems to say if the calories in don't exceed the calories out, you aren't going to gain weight.

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4. 4. Katrina RN 01:58 PM 3/19/10

   If "calories in, is calories out" is the only factor, then lets use the analogy of a car. You can put the same amount of gasoline in and it not get you as far in some cases. You have to factor in how fast you are driving, how much effort it takes to go up a mountain as opposed to flat surface, etc. It is the same with the human body. For different reasons, different bodies are more or less energy efficient. Reasons like how fast their heart beats , the size of their body, how much muscle as opposed to fat, what their temperature runs, whether they are pregnant or healing or not and how much stress they are under. "Calories in, is Calories out" may be a good baseline, but any good healthcare practitioner can reason out why that is way too simple of an equation.

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5. 5. Abraham from weight loss solutions 01:20 AM 8/4/10

   I have read in a lot of books that we should not eat carbohydrates after 3 pm (in the evening) and should not eat at all after 7 or 8 pm. Is this something this researching is trying to point to?

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6. 6. coolfatchick@gmail.com 06:26 AM 8/6/10

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