The causal role of breakfast in energy balance and health: a randomized controlled trial in lean adults. ISRCTN31521726

Background: Popular beliefs that ‘breakfast is the most important meal of the day’ are grounded in cross-sectional observations linking breakfast to health, the causal nature of which remains to be explored under real-life conditions.
Objective: To conduct a randomized controlled trial examining causal links between breakfast habits and all components of energy balance in free-living humans.
Design: The Bath Breakfast Project is a randomized controlled trial with repeated-measures at baseline and follow-up amongst a cohort in South-West England aged 21-60 y with Dual-Energy X-Ray Absorptiometry (DXA)-derived fat mass indices ≤11 kg·m-2 (women; n=21) and ≤7.5 kg·m-2 (men; n=12). Components of energy balance (resting metabolic rate, physical activity thermogenesis, energy intake) and 24-h glycemic responses were measured under free-living conditions with random allocation to daily breakfast (≥700 kcal before 1100 h) or extended fasting (0 kcal until 1200 h) for 6 weeks, with baseline and follow-up measures of health markers (e.g. hematology/biopsies).
Results: Contrary to popular belief, there was no metabolic adaptation to breakfast (e.g. resting metabolic rate stable within 11 kcal·d-1), with limited subsequent suppression of appetite (energy intake remained 539 kcal·d-1 greater than fasting; 95%CI=157, 920). Rather, physical activity thermogenesis was markedly higher with breakfast than fasting (442 kcal·d-1; 95%CI=34, 851). Body mass and adiposity did not differ between treatments at baseline or follow-up and neither did adipose tissue glucose uptake or systemic indices of cardiovascular health. Twenty-four hour glycemia was more variable during the afternoon/evening with fasting than with breakfast by the final week of intervention (2%; 95%CI=0.1, 8).
Conclusions: Daily breakfast is causally linked to higher physical activity thermogenesis in lean adults, with greater overall dietary energy intake but no change in resting metabolism. Cardiovascular health indices were unaffected by either treatment but breakfast maintained more stable afternoon/evening glycemia than fasting.

breakfast, fasting, health, energy balance

Cite this dataset as:
Betts, J., Richardson, J., Chowdhury, E., Holman, G., Tsintzas, K., Thompson, D., 2014. The causal role of breakfast in energy balance and health: a randomized controlled trial in lean adults. ISRCTN31521726. Bath: University of Bath Research Data Archive. Available from:


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James Betts
University of Bath

Judith Richardson
University of Bath

Enhad Chowdhury
University of Bath

Geoffrey Holman
University of Bath

Kostas Tsintzas
Queen's Medical Centre

Dylan Thompson
University of Bath


University of Bath
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Biotechnology and Biological Sciences Research Council (BBSRC)

Extended Daily Fasting (Omission of Breakfast) and the Regulation of Energy Balance

Publication details

Publication date: 2014
by: University of Bath

Version: 1


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Related papers and books

Betts, J. A., Richardson, J. D., Chowdhury, E. A., Holman, G. D., Tsintzas, K., and Thompson, D., 2014. The causal role of breakfast in energy balance and health: a randomized controlled trial in lean adults. The American Journal of Clinical Nutrition, 100(2), 539-547. Available from:

Contact information

Please contact the Research Data Service in the first instance for all matters concerning this item.

Contact person: James Betts


Faculty of Humanities & Social Sciences

Life Sciences
Biology & Biochemistry