by Barbara Berkeley, MD
Last year was arguably the "Year of the Microbiome" in the obesity world. Considerations of gut bacteria, its health and composition, assumed 'hot topic' status. And for the first time in many years, our attention was diverted from the endless and fruitless debate about calories. Amazing! Incredible! There might be factors entirely unconsidered which have changed us from lean beings to fat ones. Indeed, as most obesity specialists had already suspected, we might have been barking up the wrong tree entirely. Or perhaps there are just multiple trees at which to bark...not just one.
Recent hints and trends suggest that 2015 might just turn out to be the "Year of Time Restricted Eating". An offshoot of the intermittent fasting school of thought, time restricted eating suggests that our food processing mechanisms might work better if given time to reset/purge themselves after eating. This idea appeals to common sense from an evolutionary perspective. It's likely that our bodies are well-tailored to periods of food consumption followed by periods of food scarcity, conditions we would have had to face with regularity in ancient times. But how much food scarcity is needed to balance food excess? And is this an idea that translates to modern eating habits?
For some time, devotees of intermittent fasting have suggested that there are other ways to prevent weight gain/ regain besides suffering through complete days without food. Some suggest stopping all food consumption by a certain hour, while others have had success with limiting daily eating to an eight hour period.
Research from the Salk Institute in California is looking at the intriguing possibility that time restricted feeding changes an organism's response to storing fat. At least in mice this appears to be true. Researchers fed two groups of mice high fat diets. The daily diet contained the same amount of calories, but one group of mice consumed all calories within an eight hour window, while the second group was allowed access to the same food around the clock. Bottom line? The restricted mice remained lean and did not develop the metabolic consequences of over feeding (such as resistance to insulin and fatty liver). The free-feeders got fat and metabolically sick. None of these mice exercised. (And by the way, the picture that is at the top of this article is just a stock photo and not a photo of mice from this study).
A second study from Salk recently dissected some of the details, but remained highly positive about the effects of time restricted eating. In this study, well described by the New York Times Well Blog this week, mice were fat various diets including high fructose and high glucose variants. Despite these changes, weight and metabolism remained healthy in the time restricted mice and unhealthy in the free-fed mice. One group of mice was allowed to "cheat" occasionally by going off time plan. As long as the mice returned to time restriction within a day or two, their health did not suffer. There was also some reversal of obesity and metabolic parameters in free-feeders who were changed to time restricted diets after a period of time.
One important point that is omitted in the Times article is that weight and metabolic benefits were propotional to the duration of fasting. So we might believe that confining eating to eight hours rather than 12 would have greater effectiveness (assuming that any of these experiments translate to humans).
On a personal note, I have often noticed that meal flipping (eating lunch and just a light dinner), or stopping all eating at 6 pm, are very effective techniques for weight maintenance. And they appear to work even if done just a few days per week. At least for me.
So I remain very intrigued by these studies and do suspect that time restricted eating might work for people as well as rodents.
There's one way to find out.
Who's interested in spending a week or two eating within an eight or nine hour window? If you are, please send your feedback and results. I will publish all comments within a follow-up blog.