Giles Yeo: Geneticist and professor at the University of Cambridge specializing in the brain's control of food intake and the genetics of obesity; author of 'Why Calories Don't Count' and 'Gene Eating'.
What this episode covers
Giles Yeo walks through nearly three decades studying the genetics of obesity, from severe childhood obesity caused by single broken genes to the everyday biology that makes weight loss so hard. He argues there is no single right diet, that calorie labels are misleading because caloric availability shifts with cooking and processing, and that the brain actively defends a set weight range. He debunks popular ideas including the alkaline diet, widespread gluten intolerance, and the supposed healthiness of fruit juice. He closes with practical, sustainable targets (16% protein, 30g fiber, under 5% added sugar), the importance of muscle mass for healthy aging, and a mission to destigmatize obesity so policy can make healthy food cheaper.
The guest's own work
Why Calories Don't Count: How We Got the Science of Weight Loss Wrong
Giles Yeo
“his book is called why calories don't count what you eat does matter”— Steven Bartlett
Gene Eating: The Science of Obesity and the Truth About Dieting
Giles Yeo
“you've written these two fantastic books called why calories don't count and Gene eating”— Steven Bartlett
Also referenced (named, not recommended)
23andMe
23andMe
“23 me is cheap so that's probably a good place to start to ask certain questions”— guest (Giles Yeo)
Coca-Cola
The Coca-Cola Company
“orange juice or apple juice but both of those juices in particular have as much sugar concentration exactly the same sugar concentration as Coca-Cola”— guest (Giles Yeo)
Big reveals from this episode
- Everyone's brain hates losing weight: even a few pounds triggers hunger and a slight metabolism drop to drag you back to your previous weight.
- Caloric availability means cooked celery (~31 cal) yields far more calories than raw celery (~6 cal), so labels are a moving target.
- Orange and apple juice have the same sugar concentration as Coca-Cola, and juice can be worse because people think it's healthy.
- The alkaline diet is a scam: the stomach acidifies and neutralizes everything, so nothing you eat changes your blood pH.
- Only ~1% of people are celiac and 3-4% genuinely gluten intolerant, yet ~25% buy gluten-free products.
- Yeo's sustainable formula: 16% of energy from protein, 30g fiber per day, and under 5% added sugars.
- Exercise is a poor weight-loss tool for non-athletes because it makes you hungry; it works for weight maintenance.
- Muscle mass, independent of fat, is the strongest predictor of health as you age past 60.
Worth remembering
- Yeo started studying children who were three years old but weighed 100 pounds due to a broken leptin signal.
- Roughly 0.3% of people (about 1 million in the US) carry MC4R mutations making them ~40 pounds heavier by age 18.
- About 30% of protein calories are spent metabolizing the protein itself, so protein labels overstate usable calories.
- Around 65% of human adults are lactose intolerant; lactose tolerance is the mutation, arising ~7,500 years ago.
- Protein is more filling than fat, which is more filling than carbohydrate, in that order.
- Metabolism does not start dropping until around age 60; earlier weight gain comes from less muscle and more food.
- Between ages 20 and 50 the average person gains about 15 kilos (roughly one to two pounds a year).
- Worldwide we are getting fatter, and in the last decade more people die from over-nutrition than under-nutrition.
- Obesity-related illness is estimated to cost the UK economy around 27 billion pounds a year.
- Orthorexia is an obsessive fear of not eating 'properly'; a cited study found ~49% of women following food accounts on Instagram showed it.