Nutrition on GLP-1 — how to eat when your stomach has been muted

"I lost 12 kilos, I feel amazing, but my hair is falling out, my sleep is fragmented, my strength is gone in the gym, and my dermatologist says my skin has aged five years."

This is what happens when you drop a person into a 40–50% caloric deficit, mute their hunger signalling, delay their gastric emptying, and then let them eat the way they always did — soft, low-protein, carb-forward, low-volume.

GLP-1s (semaglutide, tirzepatide, liraglutide) are a powerful class of drugs. The problem is not the drug. The problem is that no one is telling people the nutrition rulebook changes on day one.

What the drug is doing to your GI tract

Central appetite suppression via hypothalamic and hindbrain GLP-1 receptors.
Delayed gastric emptying — food sits 2–4x longer than baseline.
Reduced downstream absorption of amino acids, iron, B12, calcium and fat-soluble vitamins.

At the same food volume, the body extracts less. At the same protein number on paper, tissue synthesis is lower. The person feels fine because the drug has muted the signal that used to say they are running on fumes.

What actually goes wrong

Muscle loss. STEP, SURMOUNT and SELECT trials show 25–40% of total weight lost on a GLP-1 is lean mass — roughly double a well-run non-drug deficit.
Hair shedding. Peaks around week 12–20 as telogen effluvium. Preventable.
Skin ageing. Loss of subcutaneous fat is real; the deeper issue is loss of collagen synthesis from lysine and methionine undersupply plus a glutathione drop.
Gastric stasis and reflux. Aggravated by carbonated drinks, big fat and fibre loads.
Sleep fragmentation and mood flattening. The nervous system reads sudden nutrient undersupply as low-grade threat.

The rulebook

Rule 1: Protein floor is higher, not lower

1.6–2.0g protein per kg of ideal body weight, every day. Front-load 30–40g of complete protein before 10am.

Rule 2: Complete sources only

Whey isolate, Greek yogurt, skyr, cottage cheese, eggs, chicken breast, lean beef, fish, prawns. Tofu, tempeh, edamame in one meal per day.

Rule 3: Protein first, mechanically

Whatever hits the stomach first is what actually gets digested and absorbed under delayed emptying.

Rule 4: Small, dense, more frequent

4–5 small dense meals 60–90 minutes apart. 30g of protein per meal is the absorption ceiling.

Rule 5: Fibre — cooked, not raw

Soups, stews, cooked greens, plus 1 tablespoon of psyllium husk once a day.

Rule 6: Hydration plus sodium

30ml/kg water plus 2–4g sodium daily. Brain fog on a GLP-1 is almost always sodium-depletion.

Rule 7: Resistance training 2–3x per week

Cuts lean-mass loss from ~30% to under 10% of total weight lost.

Rule 8: Four supplements everyone needs

Creatine monohydrate 5g/day; omega-3 delivering 2–3g EPA/DHA; vitamin D3+K2 tested and titrated; iron and B12 checks every 3 months.

TL;DR

Protein is life-support on a GLP-1, not a diet goal. 1.6–2.0g/kg from complete sources.
Front-load it, eat it first, keep meals small and frequent.
Lift 2–3x/week. Salt your water. Take creatine, omega-3, D3+K2. Test iron and B12 quarterly.
Nothing here is optional if you want to arrive at goal weight with your hair, skin, muscle and mood intact.

What to do this week

Weigh yourself; multiply kg by 1.8. That is your daily protein floor in grams.
Set a whey shake and a Greek yogurt on the counter tonight for tomorrow morning.
Do one 20-minute bodyweight session (squats, push-ups, rows, plank).
Salt your first glass of water each morning.
Book a blood panel: ferritin, B12, vitamin D, HbA1c.

Common Questions

Should I take an EAA powder on a GLP-1?

Yes, as a floor-setter — especially in the morning or before resistance training. See the EAA product review.

How much muscle can I actually save?

With protein at 1.6–2.0g/kg and resistance training 2–3x/week, lean-mass loss can be held under 10%.

Is intermittent fasting on a GLP-1 a good idea?

No. You already have appetite suppression and delayed emptying. Tightening the window makes hitting protein impossible.

Why does my hair keep falling out?

Caloric deficit plus protein undersupply plus iron drop plus zinc drop. Fix protein first, test ferritin, add 15–30mg zinc if intake is low.

Where this fits in the Kokorology system

This essay is the nutrition floor for the GLP-1 Anchor. It sits alongside the Skin Anchor and the Sleep Anchor. The Journal keeps protein, hydration, sodium and lift days visible in one place.

Closing

Start with the 7-Day Nervous System Reset — the €39 rail that stabilises sleep and hormonal noise around a GLP-1.
Take the 30-second Discovery to find the anchor that matches your state.
Start the Journal 7-day free trial so your protein floor and lift days are visible daily.

Sources

Wilding JPH et al. — STEP-1: Once-weekly semaglutide (New England Journal of Medicine).
Jastreboff AM et al. — SURMOUNT-1: Tirzepatide once weekly (New England Journal of Medicine).
Longland TM et al. — Higher protein during energy deficit combined with intense exercise (American Journal of Clinical Nutrition).
Phillips SM, Van Loon LJ — Dietary protein for athletes (Journal of Sports Sciences).
Kreider RB et al. — ISSN position stand on creatine (Journal of the International Society of Sports Nutrition).
Shukla AP et al. — Food order and postprandial glucose (BMJ Open Diabetes Research and Care).