Giles Yeo - How We Got the Science of Weight Loss Wrong - Summary

Below is my summary of the video, quoting and paraphrasing the content.

What is a calorie?

A calorie (small ‘c’; aka a ‘heat’ calorie) is the amount of energy to raise the temperature of 1 ml H2O by 1 °C at sea level.

A Calorie (big ‘C’; kilocalorie; kcal; aka a ‘food’ calorie) is the amount of energy to raise the temperature of 1 liter H2O by 1 °C at sea level.

Why don’t calories count?

These numbers are all different:

Caloric Availability

The amount of calories that you can actually drag out of a food vs the total number of calories in the food.

Sugar has 95% caloric availability.

Sweetcorn has less caloric availability than Corn Tortillas due to processing that makes the latter easier to digest.

Different foods make a difference.

How are calories empirically measured?

Bomb Calorimeter burns food in a sealed container and measures the temperature raise in the surrounding water.

This is different from human digestion.

The Atwater factors

Average calories per gram for fat / carb / protein measured comparing the Bomb Calorimeter result for multiple foods and the corresponding excrements of a human after eating the food. Used for all nutritional labels.

Why don’t calories count?

Caloric availability of Protein and Fiber.


Feeling of fullness / satiation: calorie of protein > calorie of fat > calorie of carb.

Food that takes longer to digest generally makes you feel fuller.


How much energy does it take to boil one liter of water?

It should be 100 kcal, by definition. This is the amount of kcal in an egg.

The usual daily diet of 2000 kcal would get 20 liters of water from 0 °C to 100 °C!

Why aren’t we boiling?


We store the energy we get from food into ATP units (triphosphate – 3 phosphates). When used they become ADP (diphosphate – 2 phosphates).

ADP + phosphate + energy = ATP

We go through our own body weight in ATP every single day!

Intermediary Metabolism

This is what we do to extract the energy from the nutrients:

Glucose and Fatty acids are organic molecules, which means they are made of Carbon, Hydrogen and Oxygen. They are interchangeable as long as you have the right enzymes to do it. They are either stored or burned. Glucose is stored as Glycogen until full, and then as Fat. Fat is storage, it releases the fat as you need it.

Protein is different. We don’t have a store of protein. Muscles are functional, not storage. If you don’t need the Protein, it needs to be converted to Fat to be stored.

The problem with Protein is that it also contains Nitrogen. The body has to remove the Nitrogen (and convert to Urea that we urinate) before converting the Protein to Fat, and this removal costs energy.

Protein calories are only 70% available. 30% are needed to handle the Protein. This factor is not included in nutritional labels.

Fat is 98% available. Simple Carbs like Sugar are 95% available. Complex Carbs with Fiber are 90% available.

Energy Balance

Energy Intake (Food Intake) = Energy Expenditure (Basal Metabolism + Physical Activity + Adaptive Thermogenesis)

The only way to lose weight is to create a caloric deficit, to absorb fewer calories than you burn.

Diets that work, work because they manage to create a caloric deficit


Why don’t calories count?

Energy consumed => minus calories lost through feces =>

=> Digested energy => minus Nitrogen loss through urine =>

=> Metabolisable energy => minus Diet-induced thermogenesis =>

=> Net metabolisable energy => minus Basal metabolic rate and Physical activity =>

=> Calorie deficit or surplus


Fiber comes almost exclusively from plants and has lower caloric availability than simple carbs.

Privilege & Calories

Ultra-processed foods go through an industrialized process that can’t be done domestically or in normal restaurants.

The problem is that this tends to strips out:

The upsides are:

The poorer you are, the more likely you are to have ultra-processed foods.

Sometimes life demands a chocolate bar, sometimes life demands a banana. The questions is: can we make a healthier chocolate bar?

Why don’t calories count?

We eat food, not calories.

If you focus on health, your weight will take care of itself.

What to count instead of calories?

Protein: about 16% of your daily energy intake.

Fiber: more than 30 grams per day.

Free sugars: less than 5% of your daily energy intake.

Meat-free days.

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Updated on 2022 Jul 14.

DISCLAIMER: This is not professional advice. The ideas and opinions presented here are my own, not necessarily those of my employer.