Conflicting Diet Advice Explained

Chapter summary

Diet advice changes every few years. The author took six months of reading to find a framework that explains why different diets work for different people.
The body uses glucose, fatty acids, protein and ketone bodies for energy. For the most part they are interchangeable.
Calories in, calories out is true. Extra food is stored as fat and eating less draws on fat. But the body regulates itself through homeostasis, so hormones decide how the balance is controlled.
Think of insulin as the primary control hormone, and fat as the body’s protection against sugar and starch.

Fatty acids are the main fuel. Heart and muscle prefer them, and the brain can use ketones.
Glucose cannot be stored because it is toxic. Glycogen holds about eight hours of energy, mostly in the liver. Only the liver can release glycogen back into the blood.
Blood holds only about a teaspoon or two of glucose, so 30 teaspoons of sugar in a “healthy” cereal, toast, jam and juice breakfast is a big load.
At rest the body needs only about 5g of glucose an hour. Once fat-adapted, you rarely need more than 150g of carbohydrate a day and many people thrive on 30 to 70g.
When glucose falls, you can use blood glucose, eat (20 minutes), draw on glycogen or release stored fat.

High blood sugar: More glucose enters fat cells and makes glycerol phosphate. Free fatty acids are converted to triglycerides, which cannot leave the cell. Result: less energy in the blood and bigger fat cells.
Low blood sugar: Less glucose enters the fat cell, less triglyceride is made, and free fatty acids return to the blood. Result: more energy supply and smaller fat cells.
The author calls this a cornerstone of why low-carb diets work.
Insulin also increases hunger. Insulin rises before a meal, blood sugar dips, and you feel hungriest just as you sit down.

Calorie view: Eat less and move more. It is true in the physics but ignores the regulation of appetite.
Hormone view: Control insulin by cutting sugar and simple carbohydrate. People then eat less without trying.
The author’s position: Both are right, but they answer different questions. Low-carb diets (Atkins, Paleo, LCHF) work better than calorie-restricted diets, especially if you are insulin resistant.
Complications: Genes, mind and social setting all modify the process. What you eat accounts for about 80% of the effect.

Butler, H. (2014) The Take-Out Diet, Unifying Conflicting Diet Advice.
Standard biochemistry texts on lipogenesis and triglyceride synthesis (see Biochemistry of Metabolism and Biochemistry of Fats and Oils on this site).