When appetite drops by a third or more, every bite has to do more work. The food that used to be a quarter of what you ate in a day is now half. The snacks that used to be a footnote are now structural. This is the part of weight management therapy that catches people out: not the weight coming off, but the quiet question of whether the body is getting what it needs while it does.
The shift, at Anova, is in how we think about it. Not eat less. Eat denser.
In 2025, four major medical societies (the American College of Lifestyle Medicine, the American Society for Nutrition, the Obesity Medicine Association and The Obesity Society) published a joint advisory on nutrition during GLP-1 therapy. It is the first guidance of its kind, and the evidence it draws together is unambiguous on a single point: when caloric intake falls by 16 to 39%, which is what happens on these medications, the food that remains has to carry more nutritional weight than it used to.
Five priorities follow from the evidence.
1. Protein first, every meal
The most consistent finding across the 2025 guidelines is that protein has to be prioritised early in each meal, because appetite often runs out before the plate does. Eggs, Greek yoghurt, cottage cheese, fish, chicken, tofu, lentils, protein at the start of the meal, before the rest.
The target most clinicians work with is 25 to 30 grams of protein per meal across three meals, and that number is not arbitrary. It reflects a per-meal threshold for muscle protein synthesis, the process by which the body repairs and maintains muscle. Below roughly 20 to 25 grams of high-quality protein in a sitting, the synthesis signal does not fire strongly; somewhere around 25 to 30 grams (about 0.4 grams per kilogram of body weight, carrying 2 to 3 grams of the amino acid leucine) the response is close to maximised, and there is little extra benefit from piling more into a single meal. Spreading protein across the day, with each meal clearing that threshold, does more for muscle than the same total loaded into one meal. This per-meal pattern matters more, not less, with age, because the muscle of older adults is less responsive to protein and needs a slightly higher per-meal dose to mount the same response. Across a day, this lands inside the broader target of 1.2 to 1.6 grams of protein per kilogram of body weight that clinical guidance now recommends during medication-assisted weight loss, well above the standard 0.8 g/kg baseline set for a weight-stable adult.
The reason this matters: without adequate protein, a substantial share of the weight lost on these medications, by some estimates around 30 to 40%, comes from lean tissue, of which roughly half is muscle. Protein on its own won’t fix that. It has to pair with resistance training, two or three sessions a week, for the muscle to have a reason to stay. Skipping the protein guarantees the loss. Pairing it with strength work is the only combination that meaningfully protects against it.
2. Fibre, in colour, with water
Slowed gastric transit is part of how the medication works, but it’s also why constipation is the most common side effect. The fibre target doesn’t change because you’re eating less: around 25 grams a day for women and 30 to 38 grams for men, which means fibre has to become a higher proportion of what’s on your plate.
Berries do this work especially well. A cup of raspberries delivers around 8 grams of fibre with under 70 calories. Oats, chia, lentils, leafy greens, and whole grains carry the rest. Two cautions worth knowing: water has to come with fibre or it can make constipation worse, not better; and during nausea flares, temporarily lowering fibre helps the gut settle. The pattern is daily fibre across baseline weeks, eased back during dose escalations or rough days.
3. The nutrients that go missing first
Observational studies of GLP-1 users at twelve months consistently find the same deficiencies in roughly the same order: vitamin D, then thiamine and other B vitamins, then iron, calcium, magnesium, potassium, and B12. These show up as fatigue, brain fog, feeling cold, hair shedding around weeks eight to twelve, and brittle nails. They are not direct medication effects. They are signs that food intake has fallen below the threshold where micronutrients can come from food alone, generally below 1,200 calories a day for women and 1,800 for men.
Eggs, dairy, leafy greens, beans, nuts, seeds, and a small amount of red meat or oily fish weekly cover most of this. A standard daily multivitamin is reasonable as a baseline safeguard against the gaps, but it isn’t a substitute for the food. A blood panel covering vitamin D, B12, ferritin, and a full electrolyte profile is a sensible check at three months in, and again at twelve.
4. Nuts, seeds, and the small dense things
When portions shrink, calorie-dense whole foods earn their place in a way they didn’t have to before. A small handful of almonds delivers protein, magnesium, vitamin E, and around 160 calories in a portion you can finish even on a quiet appetite. Walnuts add omega-3s. Pumpkin and sunflower seeds bring zinc and iron. Avocado brings potassium and monounsaturated fats. Olive oil on vegetables adds fat-soluble vitamin absorption: vitamins A, D, E, and K all need fat to be absorbed properly, so the dressing isn’t decorative.
These are the foods that quietly fix the calorie trap. A registered dietitian writing in Medscape in late 2025 described finding herself, despite her training, consuming fewer than 900 calories a day on a GLP-1 without realising it. That is below the line where even a careful diet can deliver adequate nutrition. The small dense foods are how a smaller plate stays a complete one.
5. Watch for the functional signals
The body warns before the lab does.
Persistent fatigue that doesn’t lift. Brain fog. Dizziness on standing. Feeling cold when others don’t. Hair shedding from week eight onwards. Brittle nails. Low mood that doesn’t match what’s happening in your life. These are signs that intake is too low or unbalanced, not signs that the medication isn’t working. The fix is usually nutritional, not pharmacological.
If you notice them, raise it at your next consultation rather than pushing through. A small adjustment to the food: more protein at breakfast, a daily handful of nuts, an extra cup of leafy greens, a multivitamin while bloods are checked, usually clears them within a few weeks. Pushing through doesn’t make the underlying problem go away; it just lets it accumulate.
What to try this week
Build one meal that has all five elements in it: a palm of protein, a cup of colour (berries or leafy greens), a thumb of healthy fat (nuts, seeds, avocado, olive oil), a small portion of whole grain, and a glass of water beside it. Make it the meal you’ll eat regardless of appetite, usually breakfast or lunch, when appetite is least suppressed. The rest of the day can flex around it.
The shift is in the standard, not the size. A smaller plate, eaten well, can deliver more than a larger plate eaten badly. That is the part of this work that doesn’t get said often enough.