We have a deep-seated, universal instinct to avoid unnecessary physical activity because, for millions of years, conserving energy was critical for survival and reproduction.

Instead of relying on willpower, use 'commitment contracts' like scheduling workouts with a friend or using services that create financial consequences to make exercise necessary.

Cancer can be viewed as a disease of high energy, where excess energy availability from inactivity and diet turns on growth pathways that fuel cancer cell proliferation.

The Hadza hunter-gatherers sit for about 10 hours a day, but they do so intermittently and in active positions like squatting, which is metabolically different from our prolonged, passive sitting in ergonomic chairs.

Focusing only on strength training without cardio can be as bad for cardiovascular health as being sedentary, as the heart needs the 'volume challenge' of cardio, not just the 'pressure challenge' of weights.

Modern women have around 400 menstrual cycles in their lifetime compared to about 150 in natural fertility populations, resulting in many more pulses of estrogen and progesterone that increase the risk of certain cancers.

We should avoid the 'paleo fantasy,' which is the flawed idea that everything hunter-gatherers did is a prescription for modern life, as they also didn't use vaccines or brush their teeth.

The 10,000-steps-a-day recommendation originated from a 1960s Japanese marketing campaign for a pedometer, not from scientific evidence, although it turns out to be a decent guideline.