We've all heard that we are what we eat - What if we were WHEN we ate?
Scientists spend a lot of time researching what is best for us to eat, but a lot less has been devoted to investigating when we should be doing it. You'd be quite likely to see bodybuilders and dieters splitting their energy intake over many small meals, and the health conscious fuelling their day with a big breakfast, but in general, this is an area in which a lot of people have been largely guided by their own common sense, and of course, their appetite.
The body does have it's own natural timing system, and our circadian rhythms play a big role in determining our sleeping and activity patterns. Scientists have discovered a number of genes involved in the regulation of our circadian rhythms, and recent experimental work has linked some of these to appetite, weight gain, and the development of metabolic diseases like diabetes.
Timing and food consumption is a fertile area for discovery, and a group out of San Diego has recently made a very interesting finding through research done on a population of mice.
The adult male mice were fed one of four diets which was maintained over the course of the 38 week study – High fat, high fructose, high fat and high sucrose, and a control diet.
Each group of mice was then divided further. Some mice in the group were allowed to eat whenever they wanted, but others were restricted to feeding windows of nine, twelve, or fifteen hours per day, coinciding with their most active phase. All mice ate the same number of calories overall.
Then, to mix things up, through the experiment, some of the mice in the restricted feeding groups were allowed to 'cheat' on weekends and eat whenever they wanted, and some of the mice that were on the free eating protocol were moved into the restricted eating windows over the course of the experiment.
The researchers made some striking findings. As expected, the mice eating unhealthy food at all hours became obese and developed metabolic disease, but what was surprising was that mice on unhealthy diets stayed slimmer and healthier when they ate their daily intake over a nine, or a twelve hour window than when they were allowed to eat at will, despite equivalent calories and food composition. Similarly, mice fed the healthy control diet put on more bodyfat and showed greater incidence of metabolic disease when they were allowed to eat at any time of the day than they did when consuming the exact same diet over a restricted time frame.
If you've ever felt guilty for cheating on a diet, you're going to love the fact that the slim, healthy mice who were restricted during the week but allowed to eat whenever they wanted on weekends still remained slim and healthy throughout the study, proving that doing the right thing the majority of the time overrides the odd slip up, even one that happens every weekend! By the same token, obese mice who moved from eating when they wanted onto a nine or twelve hour eating restriction managed to drop some of the weight and improve their metabolic health parameters by the end of the study.
This study has given us some pretty clear evidence that the window over which we take in our daily food intake can have a huge bearing on weight and metabolic health, and that timing may be just as significant as the food that we choose to eat. The researchers believe that this is related to our circadian rhythms and have postulated that food may be just as much of an influence on our internal body clock as light and dark.
So why are we still freaking out about carbs and chocolate, and not clambering for 5pm dinner reservations? Unfortunately, there is a lot of work to do yet. These results in mice are very encouraging, but this does not mean they will translate to people. These results need to be repeated consistently in human populations before anyone starts making recommendations.
There is a huge amount that we don't know about the circadian rhythms that rule our bodies. We can only hope this exciting research is followed up in the near future, and that it yields the same exciting results in humans as it did in mice.
Amandine Chaix, Amir Zarrinpar, Phuong Miu, Satchidananda Panda.Time-Restricted Feeding Is a Preventative and Therapeutic Intervention against Diverse Nutritional Challenges. Volume 20, Issue 6, p991–1005, 2 December 2014