How much to cut, how much to add: the calorie numbers

In the article about the phases I explained how to choose which one you should be in. What was missing were the numbers: how far to drop or raise the calories, and how fast to let the weight move.

In a deficit, the body builds less

When you eat below what you burn, muscle protein synthesis drops. A deficit around 20 per cent can cut the muscle's response to a meal by almost 20 per cent. Strength training makes up for part of it, but the response always stays below what you would get at maintenance.

Two rules of the cut come out of this, and you already know them: protein goes up and the training stays heavy. And one honest expectation comes out of it too: while you cut, the goal is to keep the muscle you have. Building is for another phase.

The pace of the cut matters

How fast the weight comes down matters as much as the deficit itself. The best-supported reference sits between 0.5 and 1 per cent of body weight per week. For an 80 kg person, that is 400 to 800 grams.

In a study with female athletes (Mero and colleagues, 2010), losing half a kilo a week was compared with losing one kilo a week, over 4 weeks. The group that went faster lost 5 per cent of their bench press strength and had a drop in testosterone 30 per cent larger.

The leaner and more experienced you are, the closer to half a kilo you should stay. Anyone with plenty of fat to lose can sit closer to the kilo.

The arithmetic never quite works out

The classic rule says that a 500-calorie daily deficit gives you half a kilo lost per week. In practice it often fails (Camps and colleagues, 2013): the body adapts to the cut and starts burning less, and that adaptation varies from person to person. The body has not read the formula.

So the initial deficit is only an estimate: between 20 and 30 per cent, higher when there is more fat to lose, lower when you are already lean. Then you weigh yourself week by week, or on your update days, always under the same conditions, and you adjust according to what the weight did.

And to build, how much do you add?

At maintenance, muscle grows very little. To build you need to eat above your burn, but less than people think:

• Someone starting now can gain 0.25 to 0.5 per cent of body weight per week and tolerates larger surpluses. A good share of the gain is muscle, because there is a lot of room for progress.
• Someone who has been training for years stays at 5 to 10 per cent above maintenance, something like 200 to 300 calories. Above that, what you gain on top is almost all fat.

Studies with bodybuilders always show the same thing: larger surpluses give more muscle and also more fat. A moderate surplus is what gives the best result overall.

What to take away

Cutting is done with a deficit of 20 to 30 per cent and the weight coming down 0.5 to 1 per cent a week. Bulking is done with a small surplus and the weight going up slowly. In both phases, the weight across the weeks tells you whether the plan is working, and you change one variable at a time.

The numbers are the starting point. After that it is about seeing how your body responds and adjusting without rushing.