How to lose weight

FWIW, here's a link to the human weight simulator designed by a mathematician at the National Institute of Diabetes and Digestive and Kidney Diseases. I've been playing with it today. That's a screenshot of one of my scenarios: energy intake and expenditure for a 30 year old male weighing 200 pounds who wants to bring his weight down to 165 in 6 months, and keep it there. My assumption is that he'd increase his physical activity by 20%. Oh, and the starting point is a diet of 2,669 calories per day. That has to be brought down to 1904 calories for six months - but if my guy can keep up the increased physical activity permanently, he can increase  his consumption to 2456 calories a day.

Here's the Times interview, worth reading for its insights that, a) we're getting fatter because food is cheaper and b) weight change takes a long time.