The science of weight loss – and why calories don’t count! | Prof. Giles Yeo

Think weight loss is all about eating less and moving more? Think again. In this episode, Prof. Giles Yeo reveals why calorie counting isn’t just inaccurate—it could actually make weight management harder. He explains why the popular “calories in, calories out” method doesn’t add up and explores how factors like genetics, brain signals, and gut health play a major role in shaping our weight.

Giles Yeo is a Professor of Molecular Neuroendocrinology at the University of Cambridge and Honorary President of the British Dietetic Association. His research focuses on the influence of genes on feeding behaviour and body weight. Giles is also the author of ‘Gene Eating’ and ‘Why Calories Don’t Count’.

Giles shares the surprising impact of ultra-processed foods on how we process calories and why losing weight often feels like a battle against our own biology. With decades of research in his back pocket, Giles shares science-backed advice to help you break free from yo-yo dieting, read calorie labels smarter, and embrace a more balanced, plant-rich diet for long-term health.

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Timecodes

01:17The quickfire round on weight myths

02:05The biggest weight loss myth revealed

03:07What are calories, really?

04:08Burning poop: a bizarre calorie experiment

08:05The woman who invented calorie counting

11:41How calories became a diet obsession

15:00Why calorie counting doesn’t work

18:56Why food quality matters more

20:05The blindspot of calorie labels

23:13We eat food, not calories

27:02Stress eating vs. stress starving

31:00Why we always have room for dessert

38:22How your gut controls your hunger

45:17Why pizza makes your brain light up

49:41Ultra-processed foods hijack your appetite

📚Books by our ZOE Scientists

The Food For Life Cookbook

Every Body Should Know This by Dr Federica Amati

Food For Life by Prof. Tim Spector

Free resources from ZOE

Live Healthier: Top 10 Tips From ZOE Science & Nutrition

Gut Guide - For a Healthier Microbiome in Weeks

Mentioned in today's episode

Long-termweight-loss maintenance: a meta-analysis of US studies, 2001,published in American Journal of Clinical Nutrition

Howdieting might make some fatter: modeling weight cycling toward obesity from a perspective of body composition autoregulation, 2020,published in International Journal of Obesity

Weight-lossoutcomes: a systematic review and meta-analysis of weight-loss clinical trials with a minimum 1-year follow-up, 2007,published in Journal of the American Dietetic Association

Dietor Exercise Interventions vs Combined Behavioral Weight Management Programs: A Systematic Review and Meta-Analysis of Direct Comparisons, 2014,published in Journal of the Academy of Nutrition and Dietetics

Diet,exercise or diet with exercise: comparing the effectiveness of treatment options for weight-loss and changes in fitness for adults (18–65 years old) who are overfat, or obese; systematic review and meta-analysis, 2015,published in Journal of Diabetes & Metabolic Disorders

Isregular exercise an effective strategy for weight loss maintenance?, 2019,Physiology & Behavior

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Episode transcripts are available here.