Why Diets Fail: The Three-Legged Stool

Chapter summary

Three legs: Diet and health depend on (1) biochemistry and hormones, including genes and the microbiome, (2) behaviour, meaning brain and mind, and (3) social lifestyle. If one leg is out of line, the stool falls over.
Research bias: Most published research studies the first leg. It tends to ignore how the three interact, which makes diet look more complicated than the principles really are.
Failure rate: About 80% of dieters weigh more two years later than when they started. If you are still lighter after two years, you are an exception.
Even illness does not change us: A Canadian study of over 5,000 people aged 50 or older found most made no major lifestyle changes after a diagnosis of heart disease, cancer, stroke, respiratory disease or diabetes, even after counselling.

Hugh lost 13kg (29 lb) by combining three things: going sugar free (from David Gillespie’s Sweet Poison), the 5:2 diet (Mosley and Spencer) and calorie logging with MyFitnessPal.
Together these made his diet low-carbohydrate and high-fat. He could not say which change mattered most.
Cutting added sugar cut carbohydrate, because sugar is hidden in bread, cereal and “low fat” foods where fat is replaced by sugar for taste.
Lower carbohydrate with the same protein leaves people less hungry, burns more fat and cuts calories.

Biochemistry: A change in diet changes the gut bacteria, which changes hunger signals.
Behaviour: Counting calories, weighing daily and fasting two days a week change how you think about hunger and portions. More protein meant less snacking.
Society: Eating with friends increases intake. Cafes display cakes and muffins. Buffets lead to overeating. A sugar-free, 5:2 lifestyle complicates socialising.

“Health is simple”: Some authors promise perfect health in three steps and then sell a subscription.
“Health is too complicated”: Others say it cannot be reduced to rules.
The author’s position: Both are partly right. The principles are simple. The practice is hard because three systems interact.
Willpower versus environment: The popular claim is that people lack discipline. The author says he had plenty of willpower and still saw how the environment and psychology make failure likely.

Plan for all three legs, not one.
Expect most short-term diets to work and most long-term results to fail.
Treat diet as change management: what is needed before, during and after the change.
Other books that fill in the legs include Weight Loss for Food Lovers (behaviour) and Salt Sugar Fat (society and industry).

Katch, V. (2013) Why is behavior change so hard? Michigan Today. michigantoday.umich.edu/a8589/
Gillespie, D. (2008) Sweet Poison. Penguin.
Mosley, M. and Spencer, M. (2013) The Fast Diet.
Blair-West, G. (2013) Weight Loss for Food Lovers.
Moss, M. (2013) Salt Sugar Fat. Random House.