The rate of weight loss is how fast your body weight drops during a diet, usually expressed as a percent of body weight per week. It helps decide how much muscle you keep during a cut.
Targets
The most cited recommendation for natural bodybuilders comes from Helms, Aragon and Fitschen (2014): about 0.5 to 1 percent per week. A later review on physique sports (Roberts et al. 2020) considers no more than 0.5 percent per week beneficial during contest prep. The leaner you are, the better the slower end fits.
The most direct comparison comes from Garthe et al. 2011: elite athletes lost either 0.7 or 1.4 percent per week. Only the slower group gained lean mass, though it took longer to get there.
Example: At 80 kg trend weight, 0.5 percent per week is 0.4 kg. Using the approximation of about 7,700 kcal per kilogram, that equals a deficit of roughly 440 kcal a day. This is a worked example, not a recipe.
Why the deficit matters
A meta-analysis by Murphy and Koehler 2022 found that a deficit of about 500 kcal a day or more prevented gains in lean mass. The percent rule fits this: for many people 0.5 percent per week lands in that range, while 1 percent sits clearly above it.
Measure it by the trend
Daily readings swing more than you lose in a week. That is why you read your rate of loss from the slope of your trend weight. The first week of a cut is distorted by glycogen and water and often looks faster than your deficit can explain.