When should you eat your main meal?

People are still very concerned about when and how often they should eat. "Should I not eat after a certain time?" people want to know. "Will eating 5 or 6 times a day help me lose weight?" It's fair to say that there's not a lot of good research to answer either question: an overview of the existing research from 2011 concluded that eating more frequently might help with glucose spikes, but the overall research into eating more often was contradictory. My standard answer for the question of how late one should be eating is that if you're having a late-night snack there's a good chance you're eating additional calories you may not need.

Other research has been more interesting. Long-time readers of our columns may remember a more recent article that showed that for women who were working on losing weight, consuming half their daily calories at breakfast rather than at dinner meant they lost more weight than those who ate half their daily calories at dinner.

Today's article (Am J Clin Nutr 2016;104:982-9) builds upon that earlier work: 69 healthy but clinically overweight women were assigned reduced-calorie diets designed for them to lose between 0.5 and 1 kilogram per week for the 12-week duration of the study. They were encouraged to increase their level of physical activity slowly up to 60 minutes per day of brisk walking five days per week, met regularly with dietitians and weight-loss counselors, and kept food diaries for 4 days of every week.

The women were randomly assigned to one of two groups: a Lunch Meal (LM) group, in which they consumed 50% of their daily calories at lunch, 20% at dinner, and the rest as breakfast and snacks, or a Dinner Meal (DM) group, in which 50% of their calories were consumed at the dinner meal and 20% at lunch time.

After the 12 weeks of the study the results are quite similar to the previous study on breakfast. Those who ate their main meal at dinner time lost an average of 4.3 kilograms (about 9.5 pounds), while those who at their main meal at lunch lost about 5.7 kilograms (about 12.7 pounds). Those who ate half the day's calories at lunch time lost 1/3 more weight than those who ate the larger dinner.

Otherwise, the results between the two groups is not particularly significant: their waist circumference, total cholesterol, and HDL (good) cholesterol all improved about the same amount. The Lunch Meal group improved their insulin resistance more than those in the Dinner Meal group, however. (Poor insulin resistance is one of the early signs of developing diabetes.)

What this means for you

The authors caution that this study was performed in women who were already motivated to join a weight-loss program, and those women received intensive counseling and daily telephone contact from dietitians. Further, this does not look at how well the women maintained their reduced weight and if that was affected by whether they continued to eat their main meal at the time assigned. If you are working on your weight with a reduced-calorie diet, however, and it fits into your lifestyle, it might be worth trying to have your main meal at lunch, with a lighter dinner.

First posted: October 5, 2016