Eating well on a GLP-1: the four things that go wrong

I am not going to argue about whether these drugs are good. They work, they work well, and for a lot of my clients they have done in eight months what a decade of effort did not. What I will argue is that they are being prescribed almost entirely without the nutrition care that ought to accompany them, and that four specific things go wrong as a result — all four preventable, none of them complicated.

One: you lose muscle along with the fat

In any substantial weight loss, some fraction of what you lose is lean mass. That has always been true. What is different with GLP-1 receptor agonists is the magnitude of the total loss and the speed of it — and in the published trial data, the lean-mass fraction has run in the region of 25 to 40 percent of total weight lost. In the SELECT and STEP body-composition substudies the numbers sat squarely in that range.

For a 45-year-old losing forty pounds, that is potentially a dozen pounds or more of lean tissue. Some of that is expected and benign — you need less structural muscle to carry a lighter body. A good deal of it is not, and skeletal muscle is where you dispose of glucose, which means losing it undermines the metabolic improvement you took the drug for.

The two interventions with actual evidence behind them are unglamorous: adequate protein and resistance training. I set a floor of 1.2 to 1.6 grams of protein per kilogram of body weight for clients on these medications, which for most people means somewhere between 100 and 140 grams a day. This is not a fashionable high-protein position; it is what the loss of appetite makes hard to hit accidentally.

Two: appetite loss is indiscriminate

The drug does not suppress your appetite for the foods you were overeating. It suppresses appetite. Clients routinely tell me that meat has become actively unappealing, that they cannot face a large plate, that they are eating 700 calories a day without trying and feel fine about it. That last part is the trap — feeling fine is not evidence of adequacy.

So the meal structure has to change shape. Fewer, smaller, denser occasions. Protein first on the plate, always, because whatever gets eaten first is what gets eaten. Liquid protein — a shake, Greek yoghurt, a soup blended with beans — when solid food is genuinely unmanageable, which on titration weeks it often is.

• Aim for 25–35g of protein per eating occasion rather than a daily total you hope to reach by evening.
• Eat the protein portion before the carbohydrate portion. On a small appetite this single ordering change is worth more than any food swap.
• Titration weeks are the hard ones. Plan for reduced intake in the four or five days after a dose increase rather than being surprised by it.
• If you cannot eat solids, drink something with 20g of protein in it. A shake is not a failure of virtue.

Three: the micronutrients quietly go

Eating 900 calories a day makes it arithmetically difficult to meet requirements for iron, B12, calcium, and folate, and I see the consequences in labs roughly six to nine months in. This is not an argument for a cabinet of supplements. It is an argument for a good general multivitamin, for actually checking ferritin and B12 rather than assuming, and for choosing dense foods when your total volume is small — which is a different skill from the one most people spent years developing.

Four: nobody plans for stopping

This is the one that worries me most. Discontinuation is common — cost, supply, side effects, insurance changes, pregnancy — and the STEP 1 extension data showed participants regaining roughly two-thirds of lost weight within a year of stopping. If the entire eating pattern for eighteen months has been "I am simply not hungry," there is nothing underneath it when the drug is removed.

So we build the pattern anyway, from month one, as though the medication were temporary. Regular meals at regular times even when appetite does not demand them. Protein and fiber targets you can name. Cooking skills. A relationship with hunger and fullness that you have practised rather than one the drug has done for you. If you are still on the medication in five years, none of that has cost you anything. If you are not, it is the only thing standing between you and where you started.

Treat the medication as scaffolding. Scaffolding is enormously useful and it is not the building.

If you are on a GLP-1 and nobody has discussed protein targets, lean mass, or an exit plan with you, that is not your failing and it is not necessarily your prescriber's either — a fifteen-minute medication visit cannot contain this conversation. It is simply a gap, and it is one a dietitian is specifically trained to fill.