02.12.2016
Randomized trial of 6 weeks adds to doubt over breakfast’s importance

by Parker Brown
Staff Writer, MedPage Today

Adults with obesity who ate breakfast were more likely to have higher levels of physical activity in the morning than their counterparts who skipped their first meal, according to a new study. But there were no differences between breakfast eaters and non-eaters in terms of weight change and most health outcomes over 6 weeks, according to lead study author Enhad Chowdhury, PhD, at the University of Bath in England.

Twenty-three adults were randomly allocated to either eat or skip breakfast, and eating was associated with greater physical activity thermogenesis during the morning, with a difference of 188 kcal per day (95% CI 40-335), but that difference disappeared within 24 hours. Energy intake was not significantly different between the two groups, and body mass increased across both groups over the study and didn’t vary by group. In addition, insulin sensitivity was slightly higher in the breakfast group, according to the authors.

Chowdhury and colleagues published their findings earlier this week in The American Journal of Clinical Nutrition.

“Despite strong public belief regarding the role of regular breakfast in human health, most evidence linking the omission of breakfast with negative health outcomes is based on cross-sectional associations and prospective cohort studies,” wrote the authors. “This is the first experiment to our knowledge to measure all components of energy balance and selected markers of metabolic control and cardiovascular disease risk in response to daily morning fasting compared with breakfast consumption.”

Fifteen of the participants were women and eight were men. All participants were ages 21-60 and had dual-energy X-ray absorptiometry-derived fat mass indices of ≥13 kg/m²for women and ≥9 kg/m² for men. Energy balance factors — including resting metabolic rate, physical activity thermogenesis, diet-induced thermogenesis, and energy intake — were measured under free-living conditions. Daily breakfast included ≥700 kcal before 11 a.m., and fasting meant zero calorie consumption before noon.

Participants weren’t paid during the study but were compensated for travel to the laboratory. Exclusion criteria included changes in physical activity habits during the study, unstable weight fluctuations, working on a shift, or being pregnant or breastfeeding.

There were no between group differences for waking times. The breakfast group reported eating 2719 kcal/d as opposed to the 2381 kcal/d reported by the fasting group, but that number was not significant (P=0.3). No differences in anthropometric factors and cardiovascular health existed between the groups. Fasting plasma glucose and serum insulin concentrations did not change over time in the two groups (P=0.3).

The authors wrote that the evidence fits in with what others have been finding recently. “Randomized controlled trials in free-living adults have begun to question the causal nature of these links between breakfast habits, components of energy balance, and health,” they wrote.

Limitations of the study include a reliance on food diaries for estimated energy intake and its small size.