When You Eat vs. What You Eat
If you eat too many calories a day, you will gain weight. What that exact number is will vary by from person to person based on such factors as their muscle mass, gender, and the amount of energy they expend. However, new research now suggests that there may be another aspect of consumption that comes into play: the timing of your meals.
The study, conducted by scientists at Brigham and Women's Hospital in Boston, found that people who tend to eat their largest meal earlier in the day lose more weight than those who eat a large meal hours later. Wilson, Jacque. "Meal times may affect weight loss success." CNN. 29 January 2013. Accessed 7 February 2013. http://thechart.blogs.cnn.com/2013/01/29/meal-times-may-affect-weight-loss-success The subjects were 420 adults enrolled in a 20-week weight loss program in Spain. They were divided into two meal time groups. One of the groups ate an early lunch every day, at some point before 3 p.m. The other group consumed their lunches later, starting after 3 p.m.
Lunch was the meal that the researchers focused on because it is traditionally the largest meal of the day in Spain. In fact, for these volunteers it accounted for approximately 40 percent of their caloric intake. This may explain why, in this particular research, meal time changes to breakfast or dinner had no effect on weight loss. But the participants who ate lunch earlier in the day had a 25 percent greater weight loss on average than their counterparts who had late-day lunches. At the end of the experiment, the early lunch eaters had lost an average of 22 pounds, compared to 17 pounds for the later diners.
In an attempt to pinpoint the hour that lunch was eaten as the deciding factor, the scientists controlled for a number of other influences including what the subject's food choices, appetite hormones, and how much sleep they were getting. Both groups were fairly equal in all of these areas, leading the researchers to note that the major difference was lunch timing.
Our internal clocks, or circadian rhythms, are on a 24-hour cycle that is well known to be responsible for our sleep-wake patterns. But the circadian system also functions within many cells of various organs in the body--including the fat cells.1 And each individual organ's circadian rhythm is subject to reprogramming when changes take place. So not only can you reset your sleep patterns by taking an overnight shift at work or traveling to another time zone, but you can apparently affect the circadian rhythm of your fat cells by eating at the wrong time, making you more susceptible to weight gain.
When blood tests were done on all of the study participants, those who ate later lunches were found to have much higher homeostasis model assessment HOMA levels than the early lunch eaters. This is a measure of insulin sensitivity based on beta cell function, and it is used to indicate diabetes.2 This confirms the findings of research from the University of Pennsylvania that has shown that normal mice became obese when their feeding schedules were drastically altered, even though their caloric intake was the same.3
It is these bodily rhythms that may play a major role in making us more efficient at digesting larger, higher carbohydrate meals earlier in the day. A healthy body can process the glucose better in the morning or early afternoon, putting it to use for energy needs rather than having it stored as fat in the late afternoon or evening.
In other countries that may spread calories more evenly throughout the day or concentrate more calories at dinner, the effects might be somewhat different. Still, common sense dictates not eating a huge, heavy meal too close to bed. It certainly couldn't hurt to eat more lightly as the day goes on. And if you do decide to try eating more of your calories in the earlier part of the day, that's not license to overload on junk food choices. Every meal should be healthy and chosen to provide nutrients and vitamins that will keep you feeling energetic and fit throughout the day.
- 1. Wang, Shirley S. "How Your Schedule Can Help (or Hurt) Your Health." Wall Street Journal. 29 March 2011. Accessed 8 February 2013. http://online.wsj.com/article/SB10001424052748704471904576228532850374342.html
- 2. "HOMA Calculator." University of Oxford. Accessed 8 February 2013. http://www.dtu.ox.ac.uk/homacalculator/index.php
- 3. Schleter, Brian. "It may not be what you eat, but when." University of Pennsylvania. 24 January 2013. Accessed 8 February 2013. http://www.upenn.edu/pennnews/current/2013-01-24/research/it-may-not-be-what-you-eat-when