Does it Matter When We Eat, or is it Just About the Calories?
For many years, when I am trying to figure out what to recommend to patients who are concerned about weight gain, I first try to learn as much as I can about their eating and activity patterns. One thing I learned early on was that many overweight people had a habit of snacking late in the evening or even during the night. For these people, I have pushed hard to get them to make one permanent change in their approach to food- not to eat anything after their supper meal (this includes alcohol). In my experience, if patients are able to abide by this “rule,” they are often quite successful in losing weight and keeping it off. I had long thought the reason for success with this approach to eating was just that people were consuming fewer calories per day. But, new data suggest, the reason may be more complicated. Maybe it is not so much the number of calories consumed, but the timing of the consumption?
When should we eat?
I want to recommend a very interesting article that appeared on page 18 of the January 18, 2015 NYT Sunday Magazine. The article was entitled,”Feeding time,” and was written by Gretchen Reynolds (the article was first published in the NYT on January 15, 2015, as a blog and was entitled, “A 12-hour window for a healthy weight”). The article summarized a new scientific study conducted at the Salk Institute and published in the December 2014 issue of the journal “Cell Metabolism.”
The most recent study was actually a follow-up of an earlier study conducted by the same group of researchers (M Hatori et. al.); the earlier study was entitled,”Time-restricted feeding without reducing caloric intake prevents metabolic diseases in mice fed a high-fat diet (first published on-line May 17, 2012: http://dx.dol.org/10/1016/j.cmet.2012.04.019). Basically, the investigators learned that if mice were fed a high-fat diet, those that were limited to eating during an eight-hour window, did not gain nearly as much weight, as those allowed to eat around-the-clock, even though the total calories consumed were the same for both groups.
What about the new study?
For the new study (A Chaix et.al.: Time-restricted feeding is a preventative and therapeutic intervention against diverse nutritional challenges. http://dx.dol.org/10.1016/j.cmet.2014.11.001), the researchers fed mice one of four diets: high-fat, high fructose, high fat and high fructose, and regular mouse feed, called kibble (whatever that is). The four groups of mice were then divided into groups based on meal timing: some of the mice were allowed to eat whenever, while others were limited to eating during periods or either 9, 12 or 15 hours. Caloric intake for all the groups was the same. So, what happened? You guessed it- the mice in the 9 and 12 hour feeding groups, did not gain weight (some even lost weight), but the others gained weight and became “sickly” (whatever that means).
Why?
The investigators hypothesized that it is all about circadian rhythms and the effect meal times have on them. Circadian rhythms are those body processes that vary during a 24-hour cycle, generally related to light and dark cycles. For example, the secretion of certain hormones, such as growth hormone, cortisol, and insulin show circadian patterns. So, maybe, eating times, can alter the secretion of these and other hormones that in turn can affect how food is metabolized?
So?
Anyway, if the effect of meal timing found in mice is also true for humans, teaching patients to try consuming most of their daily calories during a roughly 12-hour “window,” might be a scientifically sound approach to weight control. I for one, think this is pretty interesting. Check out the NYT article and see what you think.