“On the face of it, it seems preposterous to think that walking doesn’t help with weight loss. Recall that energy balance is the difference between the calories one ingests and the calories one spends. You probably burn roughly 50 calories more by walking a two-thousand-step mile than driving the same distance. So trudging ten thousand additional steps a day (five miles) will expend a respectable extra 250 calories per day.30 To be sure, those ten thousand added steps might make you hungrier, but if you snack sensibly and consume 100 calories less than you walked off, those supplementary steps will eventually amount to a deficit of about 3,000 calories a month. That amount is just shy of 3,500 calories, the supposed number of calories in a pound of fat according to a much-cited, overly simplistic, and inaccurate 1958 study.31 Further, low- to moderate-intensity activities like walking burn relatively more fat than carbohydrates (hence the “fat-burning zones” on some exercise machines).32 As a result, lots of people try to trudge away extra pounds. Biological systems such as bodies are messy, and anyone who has struggled to lose weight knows that simple theories rarely apply to the convoluted realities of weight loss. What works for one person fails for another, and while many people successfully shed pounds when they start a new weight-loss plan, satisfaction often turns to frustration as the initial rate of weight loss diminishes and then reverses. Study after study has shown that overweight or obese people prescribed standard doses of exercise for a few months usually lose at most a few pounds. For example, one experiment with the clever acronym DREW (Dose Response to Exercise in Women) assigned 464 women to 0, 70, 140, and 210 minutes of slow walking a week (140 minutes is about five added miles). Apart from their prescribed exercise, the women took about five thousand additional steps per day as they went about their normal activities. After six months, those prescribed the standard 140 minutes a week lost only five pounds, while those assigned 210 minutes lost a paltry three pounds (more on this unexpected result below).33 Other controlled studies on overweight men and women report similarly modest losses.34”