A low-calorie diet can be a safe, straightforward, research-confirmed path to weight loss. There are plenty of journals, calculators, apps, and other resources available for calculating your progress. Plus, a standard lower-calorie eating plan doesn’t typically restrict any specific foods (or their timing) as you might opt for smaller portions or lower-calorie substitutes.
Some popular diet plans take users to extremely low levels, though. The HCG (human chorionic gonadotropin) diet, for example, supplies as low as 500 calories per day. The Master Cleanse, a 10-day, liquid-only diet consisting of lemon juice, purified water, cayenne pepper, and tree syrup, also tops out at a few hundred calories per day. Other low-calorie eating plans, like the TLC diet (short for “therapeutic lifestyle changes”), hover near the 1,400- to 1,750-calorie mark, or calculate a specific number based on your gender, current weight, and goal weight.
This slash-and-burn approach to calories may come with downsides. Meticulous tracking of numbers and portion sizes can create disordered eating behavior in some people. If you have a history of an eating disorder or a problematic relationship with food, it’s best to approach calorie counting with caution; enlist the help of a therapist or registered dietitian, if possible.
Regardless of your mental health history, a super-low-calorie diet may not be sustainable in the long term. We all need calories for survival. If your body senses it’s not getting enough, it will fight the process with a mechanism known as “starvation mode.” “Starvation mode is a defense mechanism that the body uses to prevent fat loss and starvation. The idea is, your body wants to use your fat to keep you alive, so you don’t burn as many calories,” says Felix Spiegel, MD, a bariatric surgeon at Memorial Hermann Medical Group in Houston. “This lowers your metabolic rate, which means you’re using less calories. If you cut back your calories too much, it hinders weight loss.”
To prevent weight loss plateaus, Dr. Spiegel recommends a goal of 1 to 2 pounds lost per week. “If you lose more than that, you’re losing body fluid and muscle mass.”
