How We Set a Carbohydrate Target From Lean Mass

Most carbohydrate advice is a percentage of calories or one flat number for everyone. We set the carb target by lean body mass, because lean mass is the tissue that actually uses carbohydrate.

Why lean mass and not body weight

Carbohydrate is stored as glycogen, almost all of it in muscle, with a smaller reserve in the liver. A typical adult holds roughly 300 to 500 grams in muscle and about 100 in the liver. Muscle glycogen fuels a hard lift, a tempo run or anything above an easy pace. Fat tissue stores almost no glycogen and burns very little carbohydrate.

So two people who both weigh 200 pounds can have very different carbohydrate needs. One with 150 pounds of lean mass has a large tank to fill and drain. One with 110 pounds of lean mass has a smaller tank, and the extra 40 pounds of fat uses very little carbohydrate. Set the target by body weight and the second person gets more than he can store. The surplus is either burned instead of fat or stored as fat.

This is the same reason protein is set by lean mass. Both numbers come from a body composition scan, DEXA or InBody, not from the bathroom scale.

The range: 1 to 2 grams per pound

We set carbohydrate at 1 to 2 grams per pound of lean mass per day, and activity decides where in the range someone sits.

• Near 1 gram: mostly sedentary, training lightly a few days a week, or actively cutting fat.
• Around 1.5 grams: the default for someone lifting three or four days a week with some cardio.
• Near 2 grams: heavy endurance volume or two a day training. A marathon build or long cycling block can need more than this range, and we go above 2 when the training calls for it.

A hypothetical woman with 115 pounds of lean mass training four days a week would land near 1.5, or about 170 grams of carbohydrate a day. A man with 160 pounds of lean mass lifting and riding most days would sit near 2, or roughly 320 grams.

Protein is set first, at 1 gram per pound of lean mass. Fat lands at about 25 percent of total calories. The calorie total is what those three add up to, not a number picked in advance.

How it shifts with training

The multiplier is not fixed for the year. A rest week drops toward 1. A race build climbs toward 2. Someone cutting body fat while keeping strength sits at 1 and holds protein steady, so the deficit comes out of carbs and fat rather than muscle. Lean mass changes too, which is why the scan gets repeated and the targets rebuilt.

It is simple arithmetic, but it ties the number to the tissue that does the work. That's how we set it.

This article is educational and is not medical advice.

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