Why do 90% of dieters regain the weight yet we keep turning to diets over and over again? The answer doesn’t lie in willpower or in sugar addiction or in the irresistibility of food additives. It lies in the nature of diets themselves.

First off, the diet industry thrives off promoting unrealistic (and often unhealthy) physical ideals. It makes a whole lot of promises about those ideals it knows it can’t keep. Regardless of whether they involve calorie counting, carb cutting, or fasting, essentially all diets drastically reduce the amount of calories that you eat so that you are consuming fewer calories than you burn. This is the weight loss equation: calories in < calories out.

The thing is that diets cut your calories to an unsustainable low to make sure you lose weight faster. However, you cannot sustain at those levels long-term. The adult body is not made to run off of 1200 calories – in fact, that amount is more suitable for a toddler. What happens in response to such low calorie intake over time? Cravings, obsessing over food, binging. Plus, your body slows down your metabolism in response to those reduced calories so that you must eat less and less in order to maintain (check out this great breakdown of your body’s adaptation to calorie restriction by Precision Nutrition).

When you deprive your body of energy (calories), nutrients, and the foods you enjoy, it’s not a matter of willpower. It’s basic human biology that makes you gain that weight back. It’s not a personal failing. Diets are made for weight loss, not maintenance, not keeping it off.

So, why do dieters regain the weight they lost? Because that’s what diets are designed for. So, please, keep that in mind before you sign up for your next weight loss challenge or before you start to beat yourself up for “falling off” your diet.

Want to learn more: check out my post on the difference between dieting and healthy eating.