Calorie Deficit

A calorie deficit is the only scientifically proven mechanism by which the body reduces its fat stores. Regardless of whether you follow a low-carb, vegan, or intermittent fasting diet, weight loss always occurs through a calorie deficit. One kilogram of fat contains approximately 7700 kcal of energy, so a daily deficit of 500 kcal leads to approximately 0.5 kg of weekly fat loss.

A moderate calorie deficit is 300-500 kcal per day. This is a sustainable and safe level that doesn't cause significant hunger, fatigue, or muscle loss. Too large a deficit - over 1000 kcal per day - causes many problems: metabolism slows down, muscle mass is lost, hormone function is disrupted, hunger hormones increase, and moods fluctuate. This often results in the yo-yo effect, where lost weight returns and often with extra on top.

Practical example: if your TDEE is 2200 kcal, eating approximately 1700-1900 kcal per day puts you in a moderate deficit. The deficit can be created either by eating less, exercising more, or a combination of both.

An important insight is that the calorie deficit doesn't need to be identical every day. A consistent deficit at the weekly level is sufficient. For example, you can eat a bit more on weekends and less on weekdays, as long as the weekly total is correct. This flexibility makes weight loss more sustainable and reduces the risk of emotional eating. Calorie deficit is directly connected to TDEE, macros, and BMR.

Last updated: March 30, 2026