Starvation Mode: How Caloric Restriction Affects Your Body

The concept of starvation mode is that when you restrict calories, your body has a “hold it right there” response. To prevent you from losing weight rapidly, your metabolism slows, conserving energy by reducing the calories it burns.
Research shows starvation mode — formally called adaptive thermogenesis or metabolic adaptation — is a legit phenomenon. It’s well documented that sometimes, the more weight you lose (and the more rapidly you do so), the more your body resists the process.
Evolutionarily speaking, this may be a holdover from when humans faced food scarcity and needed a mechanism for self-preservation. But in today’s world, starvation mode can be a frustrating roadblock to weight loss.
Starvation mode isn’t the same thing as actual starving. In today’s modern food environment, true starvation is rare. If you’re eating regularly, you won’t experience life-threatening starvation.
However, your body might exhibit some of the same early signs as real starvation. These include the symptoms listed above.
Most commonly, though, starvation mode involves stalled weight loss. You may have hit the wall of adaptive thermogenesis when restricting calories and increasing physical activity without losing weight.
Getting into starvation mode can take just a few days, especially if those days involve severe calorie restriction.
So what counts as severe calorie restriction? Many experts advise not going below 1,200 calories per day for women and 1,500 calories per day for men unless supervised by a doctor. Anything below these numbers could land you in starvation mode faster.