The causal role of breakfast in energy balance and health: a randomized controlled trial in obese adults

Abstract

Background: The causal nature of associations between breakfast and health remain unclear in obese individuals.Objective: We sought to conduct a randomized controlled trial to examine causal links between breakfast habits and components of energy balance in free-living obese humans.Design: The Bath Breakfast Project is a randomized controlled trial with repeated measures at baseline and follow-up among a cohort in South West England aged 21–60 y with dual-energy X-ray absorptiometry–derived fat mass indexes of ≥13 kg/m2 for women (n = 15) and ≥9 kg/m2 for men (n = 8). Components of energy balance (resting metabolic rate, physical activity thermogenesis, diet-induced thermogenesis, and energy intake) were measured under free-living conditions with random allocation to daily breakfast (≥700 kcal before 1100) or extended fasting (0 kcal until 1200) for 6 wk, with baseline and follow-up measures of health markers (e.g., hematology/adipose biopsies).Results: Breakfast resulted in greater physical activity thermogenesis during the morning than when fasting during that period (difference: 188 kcal/d; 95% CI: 40, 335) but without any consistent effect on 24-h physical activity thermogenesis (difference: 272 kcal/d; 95% CI: −254, 798). Energy intake was not significantly greater with breakfast than fasting (difference: 338 kcal/d; 95% CI: −313, 988). Body mass increased across both groups over time but with no treatment effects on body composition or any change in resting metabolic rate (stable within 8 kcal/d). Metabolic/cardiovascular health also did not respond to treatments, except for a reduced insulinemic response to an oral-glucose-tolerance test over time with daily breakfast relative to an increase with daily fasting (P = 0.05).Conclusions: In obese adults, daily breakfast leads to greater physical activity during the morning, whereas morning fasting results in partial dietary compensation (i.e., greater energy intake) later in the day. There were no differences between groups in weight change and most health outcomes, but insulin sensitivity increased with breakfast relative to fasting. This trial was registered at www.isrctn.org as ISRCTN31521726.

Is breakfast the most important meal of the day?

“…This finding in obese deficit than lean individuals under free-living conditions (37) . Interestingly, in our experiments the 274 same obese individuals undertook both the acute investigation described earlier (where there was 275 no compensation observed at lunch) and the free-living assessments (where there was no 276 difference in daily intake between groups) (15,26) . This is in contrast to the equivalent lean 277 individuals who displayed limited compensation for breakfast omission both inside and outside 278 the laboratory (14,25) .…”

“…was not significantly different between the breakfast and fasting groups, with those assigned 269 breakfast intake consuming 338 kcal/d more (95% CI: -313, 988) (15) . This finding in obese deficit than lean individuals under free-living conditions (37) .…”

“…In contrast, it was the fasting group in the obese population who exhibited the greatest compensation, with avoidance of 173 weight-loss despite consuming not a single calorie until midday everyday for 6 weeks; whereas 174 the obese individuals in the breakfast group clearly did not compensate by expending the 175 prescribed energy intake (or reducing subsequent energy intake sufficiently) and so increased 176 energy storage in the form of adipose tissue (15) .…”

“…Changes in DEXA-derived body composition amongst lean (14) and obese (15) 161 adults over 6 weeks with either ingestion of ≥700 kcal before 1100 h daily (Breakfast Group),…”

“…The results of our 6-week interventions in both lean (14) and obese (15) of food. Different macronutrients induce varying levels of thermogenesis (49,50) but DIT is only 320 ever a fraction of the energy content of the foods ingested and typically only 10% of intake 321 when consuming a normal mixed diet (51) .…”