Professor Keith Frayn, PhD ScD, Emeritus Professor of Human Metabolism, Radcliffe Departmentof Medicine, University of Oxford

Winner of the British Nutrition Society's first-ever Blaxter Award and author of an acclaimed newbook.

We all know someone who seems to eat very little yet cannot avoid weight gain, or someone whoeats everything they like while remaining slim. Why? The last 10 years have seen increasingchallenges to the simple model of ‘calories in = calories out’. Even specialists are nowquestioning the forces that shape body weight. In this cutting edge talk, Professor Frayn takesus on a deep dive into the real science of energy balance. He provides a clear-eyed perspectiveon current trends mired in controversy and confusion: time-restricted eating, intermittent fasting,low-carb versus low-fat meal plans, high-protein breakfasts and other dietary fads. He shows usit is possible to reshape our lives and improve health by going back to what is known aboutcalories and getting smart about what to eat.

Vote of thanks by Dr Phil Duffey

On a dreary, wet night in York Professor Frayn served to the members of YMS a rich intellectual meal. During the first course we were reminded of the primacy of the first law of thermodynamics and the traditional ‘calories in - calories out’ model of weight regulation which asserts that calories unused for the maintenance of life and additional activities are stored in the form of fat. Professor Frayn then acknowledged that this model is under unprecedented challenge and in the main course expanded on some of the reasons for this and common misconceptions concerning weight and metabolism.
Professor Frayn explained that many of the earlier studies in this field had determined calories-in by recollection or diary entries. These had led to the suggestion that weight gain might be the consequence of a ‘slow metabolism’. Ultimately this was shown to be incorrect.  It was established that studies of this sort invariably under-report intake and that individuals with overweight tended to under-report by a greater margin. Professor Frayn then showed how metabolic rate can be estimated better by using radiolabelled hydrogen isotopes.
Next there was discussion of the energetics of obesity and the greater expenditure in the overweight plus the body’s response to dieting and calorie restriction, including the seminal work of Ancel Keys. We learnt that weight loss through dieting is difficult in part because energy expenditure is diminished in response to the diminished intake through the action of Leptin on the thyroid gland. These observations led to a wider review of weight regulation including genetic factors, the hypothalamus, an increasing number of hormones, particularly Leptin and Glucagon-like peptide-1 (GLP-1) and Set-point theory which Professor Frayn described as entrenched, vigorously defended and a myth!
As might have been anticipated there was no shortage of questions and comment. Many in the audience were particularly conscious of the social and economic factors influencing the eating behaviour and weight of their patients and themselves. A lively discussion continued over supper where Professor Frayn and his wife proved themselves easy and engaging conversationalists keen even to assist with the washing up.
Overall a great success.