How many calories should I eat to lose fat?

• BMR, about 60 to 70%: what your body burns just to stay alive at rest. More muscle raises it.
• NEAT, about 15 to 30%: everyday movement that isn't a workout: walking, chores, standing, fidgeting. It varies the most between people.
• Exercise, about 5 to 10%: planned workouts. Helpful, but a smaller share than most people think.
• TEF, about 10%: the energy used to digest food. Protein takes the most.

Find your number. Use the free NIH Body Weight Planner at niddk.nih.gov/bwp. Enter your age, sex, height, current weight and normal activity level. The calories it shows to maintain your weight are your estimated TDEE. It's an estimate, so your real results over a few weeks are the true answer. Recheck it every 10 to 15 lbs you lose, because TDEE drops as your weight drops.

Belle's rules for a calorie deficit

• Deficit: 300 to 500 calories a day below your TDEE.
• Pace: about 0.5 to 1% of your body weight per week (for a 180-lb person, roughly 0.9 to 1.8 lbs a week). The first weeks on medication are often faster; after that, losing much faster usually means losing more muscle, and rapid loss raises the risk of gallstones.
• Floor: don't go below 1,200 calories a day unless your provider has told you to. Going lower makes it hard to get enough protein and nutrients, costs muscle, and is hard to stick with.

The simple math. A pound of body fat holds about 3,500 calories, so a 500-calorie deficit every day for 7 days is about 1 lb of fat a week, in theory. Your body won't follow the math exactly week to week (see What results should I expect, why does the scale jump around, and what if I plateau?).

On a GLP-1, the bigger risk is eating too little, not too much. If your appetite is so low that you're regularly under 1,200 calories or can't reach your protein minimum, tell your care team.

Do I have to count calories? No. For most people, tracking daily protein is enough. Counting calories is optional: useful if you like the detail or you've stalled, but never required.

For recipes and food guidance from our dietitian, Megan, join the free Belle Community: see "What is the Belle Community, and how do I join?"