It was not you

This is the key I wish someone had handed me at twenty-five.

In 1953 a British physiologist, Gordon Kennedy, proposed that the body defends a weight the way a house defends a temperature, with a thermostat. In 1995 three researchers at Rockefeller University, Rudolph Leibel, Michael Rosenbaum and Jules Hirsch, proved it in people. After you lose about ten percent of your weight, your body burns roughly fifteen percent fewer calories than a person who was always that size, and it keeps doing that for years. Hunger goes up. Burn goes down. The weight comes back. Not because you failed. Because the thermostat worked.

Every diet you have tried and regained was fighting that.

The mechanism is in the hormones. When fat falls, a signal from fat falls with it, and the brain reads that as famine and responds the way it has for a hundred thousand years: it makes you hungrier and cheaper to run. The body cannot tell a diet from a drought.

Here is the hopeful part, and it is also in the research. The thermostat is not fixed. It moves slowly, and it moves for reasons that are not dieting: muscle, which burns at rest; sleep, which sets the hunger signal; and time spent at a new weight, which the brain gradually accepts as home. That is why the body keys this year go muscle and sleep before the plate.

I put this key in the month called You for one reason. Most people carry their diet history as a list of personal failures. Read the science and it turns into a list of a body doing exactly what bodies do. That is a different story about you, and it is the true one.