Obesity is an epidemic that’s not resolving anytime soon. It affects 42% of US adults and increases the risk of diabetes, cardiovascular disease, metabolic syndrome, inflammatory conditions, dementia, cancer and early death. Many people seek weight loss to improve quality and length of life (health span and life span, respectively), as well as to decrease their healthcare costs.
Obesity-related research plays a large role in identifying efficacious weight loss and weight-loss maintenance strategies, as well as helping to guide clinicians and patient care.
A 2013 study explored whether time of day and calorie intake influenced weight loss efforts over a 12-week period.
Ninety-three overweight/obese women with metabolic syndrome but without any other serious medical conditions were followed.
Each participant was randomized into one of two groups: high-calorie breakfast (BF) or high-calorie dinner (D). Regardless of group, each woman was instructed to follow a 1400-calorie weight loss diet – high protein (41%), low carb (32%) - and was provided coordinating meal plans.
The BF meal plan provided: a 700-calorie high-protein (54g) breakfast, a 500-calorie lunch and a 200-calorie dinner.
The D meal plan provided the opposite: a 200-calorie breakfast, a 500-calorie lunch, and a 700-calorie high-protein (54g) dinner.
Those who did not comply with the specified calorie and meal requirements at a weekly average of 42.9% or above (or about 3 days a week) were withdrawn from the study.
Measurements such as blood pressure and weight were recorded every two weeks, whereas waist circumference was obtained at baseline, week 6 and week 12. Blood biomarkers - serum glucose, insulin, lipids, and plasma ghrelin - were obtained at baseline and 12 weeks.
Dropout rates mainly due to noncompliance were higher in the D group, possibly indicating less sustainability of that calorie-time distribution.
Both groups lost weight, however, the high-calorie breakfast eaters (BF) lost significantly more than the D group, 19 and 8 pounds, respectively – a 2.5-fold increase for the BF eaters. Waist circumference was also reduced more in the BF group. Blood pressure improved similarly in both groups.
Biomarkers also improved more in the BF group. Triglyceride levels improved by 33% in the BF group whereas they increased by 13% in the D group. Fasting glucose, insulin, and HOMA-IR – a marker of insulin sensitivity – all showed more significant improvements in the BF group.
Mechanisms or theories that explain biological advantages for a larger, high-calorie, high-protein breakfast and smaller dinner include: circadian rhythms, biological clocks affected by food intake, improved insulin sensitivity in the morning, delayed lipolysis (fat breakdown) in breakfast skippers, and the ability for breakfast protein to reduce hunger hormones and extend feelings of fullness.
A 2015 study highlighted that regular breakfast-eating women who start to skip breakfast show signs of worsened metabolic responses to lunch and metabolic dysfunction. This may have played a role in the metabolic disadvantages seen in the D group women.
The ideal diet, or what you eat, is hotly debated by experts around the world, often at the expense of considering how much when you eat impacts health. This study appears to have answered the question, “Do calories, nutrients and time of day matter for weight and health?” According to these findings, consuming a large high-protein breakfast + a small dinner rather than a small breakfast + large high-protein dinner is a more effective strategy for both weight loss and improved metabolic health.
This study finds that overweight/obese women with metabolic syndrome benefit significantly more from eating a larger high-protein breakfast and smaller dinner rather than the reverse.
Weight, waist circumference, triglycerides, fasting insulin, and HOMA-IR all improved more in women who ate the larger breakfast, not the larger dinner.
Many biological mechanisms can help explain why a larger breakfast and smaller dinner is biologically superior. Examples include circadian clocks and enhanced insulin sensitivity in the morning.
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Jakubowicz, D., Barnea, M., Wainstein, J., & Froy, O. (2013). High caloric intake at breakfast vs. dinner differentially influences weight loss of overweight and obese women. Obesity (Silver Spring, Md.), 21(12), 2504–2512.
National Institute of Health. Overweight and Obesity Statistics.
Thomas, E. A., Higgins, J., Bessesen, D. H., McNair, B., & Cornier, M. A. (2015). Usual breakfast eating habits affect response to breakfast skipping in overweight women. Obesity (Silver Spring, Md.), 23(4), 750–759.
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