Agree with it or not there are some thinking points in Gary Taubes’s newest book, Why We Get Fat,  about the calorie expenditure model of weight loss.

The existing and anecdotally obvious model says that in order to lose weight we must eat fewer calories than we expend through physical activity. Put fuel in and if you need more before the day is up, you will burn what you have stored in the past. Makes sense if humans work in the same way  as machines.   Taubes points out a very interesting flaw in this thinking. His argument goes like this:

500g of fat is equivalent to 3500 calories. According to the theory, if you want to lose a pound a week, you should reduce your calories eaten by 500 per day. Seven days times 500 calories is 3500 calories. Voila! You will lose half a kilo every week as long as you keep it up.

The interesting part comes in when you start to think about what it would take to go from being a lean 25 year old to an obese 50 year old. If you gained a kilo per year you’d increase your weight by 25 kilos by your 50th year. What would that take, according to this theory? How much of a glutton would you have to be every day to make this happen? An extra 20 calories a day. That’s all! 3 bites of an apple, a sip of coke, a bite of a croissant. At less than 1% of the recommended intake for a middle aged woman whose daily activity level is described as cooking and sewing and less than 1/2% for an equally sedentary man it would be impossible to manage. Just one bite too many and it’s all over.

Does it really make sense to think of our bodies like engines? What if things were as simple as that but in a completely different way? Until recently in our history no one ate according to calories and millions of people managed to stay lean. Were millions of people getting that lucky and hitting the exact caloric mark that was right for them? Would you be willing to let go of the idea of calories?

There is no doubt that eating less results in weight loss but given that the majority of people have relatively stable weight throughout their lives is it likely that they are managing their calorific intake so exactly over the years or could there be another mechanism at work?

Have a read of the book and post your thoughts here.