Is It Time to Eat? A Surprisingly Important Question

'Tis the season for making New Year's resolutions.  Perhaps your resolutions include healthier eating and losing weight.  There is certainly plenty of info in my past articles on how to construct a healthy diet that will help you live longer and prevent chronic diseases. One element that may have been overlooked in all the scrutiny over what to eat is when to eat. There is growing evidence that restricting our eating to certain times of the day leads to more easily maintaining a healthy body weight.

Several authors and experts have been touting so-called "intermittent fasting," which consists of only eating between the hours of 10 AM and 6 PM, for example. Another version of this approach involves eating normally five days per week, but essentially fasting (taking in less than 500 calories) on the other two days.  The idea behind this is that a more prolonged period without food discourages fat storage, and allows our body to switch its metabolism over to burn our stored fat supplies.

A recent study in mice (1) seems to support this idea. In this study, two groups of mice were allowed to eat as much as they wanted. One group had food available at all times, while the other group only had food available for a 12-hour period each day. The group with the more restrictive time ate about the same number of calories as the other group, and yet maintained a healthy body weight, while the unrestricted group became obese.  The time-restricted mice were even able to reverse obesity and prevent type-2 diabetes.  Cholesterol balance improved within two weeks, and blood sugar control improved within a few days.

A related study (2) showed how this intermittent fasting can change the composition of the gut microbiome.  A healthier blend of friendly intestinal bacteria leads to leaner body weight.

It's too soon to translate these results directly to humans, but there have been some small human studies that point to the benefits of this approach.  One study found that intermittent fasting led to the same amount of fat loss as traditional calorie-restricted diets, but preserved much more healthy lean tissue. (3)

In a way, all of this seems to hearken back to traditional Chinese and Ayurvedic medicine: these systems used more poetic language to recommend against eating late into the evening or at night.  Whatever the reasoning, the outcome seems to be the same -- better health when we pay more attention to eating at the right time of day.

Listen to an interview with one of the researchers:  You Are 'When' You Eat 

1.  Amandine Chaix, Amir Zarrinpar, Phuong Miu, Satchidananda Panda.  Time-Restricted Feeding Is a Preventative and Therapeutic Intervention against Diverse Nutritional Challenges.  DOI: http://dx.doi.org/10.1016/j.cmet.2014.11.001

2.  Amir Zarrinpar, Amandine Chaix, Shibu Yooseph, Satchidananda Panda.  Diet and Feeding Pattern Affect the Diurnal Dynamics of the Gut Microbiome.  DOI: http://dx.doi.org/10.1016/j.cmet.2014.11.008

3.  Intermittent fasting vs daily calorie restriction for type 2 diabetes prevention: a review of human findings.  Transl Res. 2014 Oct;164(4):302-11. doi: 10.1016/j.trsl.2014.05.013. Epub 2014 Jun 12.

Another Secret to a Smaller Waistline

There has been a lot of speculation about the increasing rates of obesity over the last few decades.  Many of the causes of this phenomenon are well known, and I have covered them in past articles: the move from whole foods to more processed foods, a decrease in physical activity with the rise in technology, and the increasing intake of both regular and diet soda pop.  One factor that often gets overlooked in this equation is the importance of a good night's sleep.

Researchers in the UK (1) recently published the results of a survey of over 100,000 women covering a 10 year period.  They found that light exposure at night disrupted the normal circadian rhythm (day-night cycle), and led to increased body mass index, and increased waist circumference.

If you are trying to shed pounds by increasing exercise, then bravo!  Just don't exercise late in the evening.  Night should be a time for winding down, decreasing activity, and definitely minimizing exposure to light (no falling asleep with the TV on).  The infographic below is a handy reminder of what's known as good sleep hygiene.  Use it to optimize your sleep, and maintain a healthier body weight.

1.  McFadden E et al.  The Relationship Between Obesity and Exposure to Light at Night.  Am J Epidemiol. 2014;180(3):245-250.

Did You Enjoy that Extra Hour of Sleep this Weekend?

Welcome back to standard time, folks... did you remember to set your clocks back this weekend?
One more question:  did you notice it was much easier to adjust to the time change this weekend than to the switch to daylight savings time in the spring?  It seems logical, since we "gained" an hour of sleep on Saturday night.  But even beyond that, this is the one weekend out of the year when the external clocks match most closely to our internal biological clocks.

Yes, we do have a biological clock -- a part of the brain called the suprachiasmatic nucleus (SCN); its job is to keep track of the daily cycle of our body's functions (also known as our circadian rhythm).  Research has shown that for most folks, the SCN is actually set to a 25-hour cycle, which means that we have to reset it every day based on cues in our environment.  That's why it's easier to stay up late, but harder to wake up earlier in the morning.

Up till about 200 years ago, our biological clocks mostly relied on the signals of sunlight to reset ourselves each day.  With the advent of reliable timekeeping, we now go by a strict 24-hour day; with electric lights, we can give in to our tendency to want to stay up later, if we choose.

Use the "extra" sleep you got this weekend to honor your body's natural circadian rhythm.  Don't complain about the early sunset, but rather use it as a signal to get to bed at a reasonable time -- and enjoy the earlier sunrise these days.  Sleep is one of the foundations of health, and most adults need around 7-8 hours per night.  Getting adequate sleep helps not only with our daytime energy, but also with preventing diabetes, cardiovascular disease, and obesity.

This is a repost of an article that appeared in 2011.