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GLP-1 tool

TDEE on a GLP-1

A GLP-1 lowers your appetite, not your energy needs, so the gap between what you burn and what you eat can get bigger than you'd plan on purpose.

Clinician review pending Updated

How to use it

  1. Step 1Enter your sex, age, height, weight and activity level.
  2. Step 2Slide to how much you eat now compared with before treatment.
  3. Step 3Read your estimated intake, daily deficit, weekly loss and protein floor.

Explainer · 0:21

STEP 1 · RESTING BURN BMR (Mifflin-St Jeor) 1,528 kcal/day woman · 35 · 5 ft 6 in · 180 lb STEP 2 · ADD MOVEMENT BMR + everyday activity × 1.375 2,101 kcal/day = TDEE STEP 3 · SET A DEFICIT TDEE minus 500 −500 1,601 kcal/day target STEP 4 · WHAT TO EXPECT 180 lb ~1 lb a week at first slows over time week 0week 30 0:21 · voiced · captions on
Your body burns energy even at rest. That's your BMR: about 1,528 kcal a day for a 35-year-old woman who is 5 ft 6 in and 180 lb.
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How your daily calories are worked out
Read the transcript
  1. Your body burns energy even at rest. That's your BMR: about 1,528 kcal a day for a 35-year-old woman who is 5 ft 6 in and 180 lb.
  2. Daily movement multiplies it. Light activity is × 1.375, so 1,528 becomes about 2,101 kcal. That's your TDEE.
  3. Eat about 500 kcal less than your TDEE and you're in a deficit: around 1,601 kcal a day.
  4. That's roughly 1 lb a week at first. Loss slows as your body adapts, so treat the number as a starting point and adjust.

The calculation

TDEE uses Mifflin-St Jeor and your activity multiplier. Estimated intake = TDEE × your appetite percentage. Deficit = TDEE − intake. Weekly loss ≈ deficit × 7 ÷ 3,500.

Worked example: TDEE 2,101 kcal, eating 65% of usual: intake about 1,366 kcal, a 735 kcal deficit, roughly 1.5 lb a week at first.

Why protein and fluids come first

When intake drops this much, protein is easy to miss. The tool shows a floor of 1.2 g per kg of body weight and warns if intake looks below 1,200 kcal (women) or 1,500 kcal (men). Very low intake is worth telling your prescriber about.

This assumes your old intake roughly matched your TDEE. Early weekly drops also include water. See What to eat on a GLP-1.

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Common questions

How many calories should I eat on Zepbound or Wegovy?

The labels don't set a calorie target. Many clinicians focus on enough protein, fiber and fluids rather than a strict number.

Is it bad to eat very little on a GLP-1?

Eating far below your needs can cost muscle and make it hard to get nutrients. Tell your prescriber if you're regularly eating very little.

Why am I losing weight so fast on a GLP-1?

A smaller appetite can create a large deficit, and early loss includes water. Loss usually slows over time.

Does TDEE change as I lose weight?

Yes. It drops as your body gets smaller, so recalculate every 10 to 15 lb.

Sources

  1. Mifflin MD et al. A new predictive equation for resting energy expenditure. Am J Clin Nutr 1990
  2. Jastreboff AM et al. Tirzepatide once weekly for the treatment of obesity (SURMOUNT-1). NEJM 2022
  3. Wilding JPH et al. Once-weekly semaglutide in adults with overweight or obesity (STEP 1). NEJM 2021

Clinician review pending. Drafted from primary sources and waiting for sign-off by a licensed clinician (MD, DO or PharmD) before launch. Every number is checked against its source. Drug facts are re-checked quarterly, prices monthly and whenever a label changes. How we review · Report an error