Protein, fiber & food quality

Protein helps fat loss three independent ways. Satiety: it raises the same fullness hormones the drugs target (GLP-1, PYY, CCK) and lowers ghrelin — in one trial, raising protein to 30% of calories cut spontaneous intake by ~440 kcal/day with no conscious restriction. Thermic effect: 20–30% of protein calories are burned just digesting it, vs ~5–10% for carbs and ~0–3% for fat. Muscle: it preserves lean mass in a deficit. Evidence ●●●●●

Roughly 1.6 g/kg body weight per day is the floor for holding muscle while training; pushing to 1.6–2.2 g/kg (or up to ~2.3–3.1 g/kg of lean mass) helps most when the deficit is steep, you’re lean, older, or on a GLP-1 drug. Spread across 3–4 meals of ~25–40 g. Powder is just convenient food to hit the target, not a fat-burner.

High protein does not harm healthy kidneys — a meta-analysis of 28 trials found no effect on filtration rate. The transient rise sometimes cited as ‘damage’ is normal, reversible adaptation. The genuine exception is pre-existing kidney disease, where protein should be managed with a clinician.

Viscous fibers form a gel that slows gastric emptying and blunts glucose spikes; fermentable fibers feed gut bacteria that produce short-chain fatty acids, which stimulate the satiety hormones GLP-1 and PYY. Net effect: fuller on fewer calories. Adding ~14 g/day of fiber is associated with ~10% lower energy intake and ~1.9 kg loss over four months.

Target is ~25 g/day (women) to ~38 g/day (men); typical intake is only ~15 g. It is one of the cheapest levers available. In one trial, the single instruction ‘eat ≥30 g fiber/day’ delivered ~78% of the weight loss of a far more complex prescription. Evidence ●●●●○

The strongest causal evidence here is a metabolic-ward study (Hall 2019): 20 adults ate freely from ultra-processed vs minimally-processed diets matched for calories, sugar, fat, salt and fiber. On the ultra-processed diet they ate ~500 kcal/day more and gained ~1 kg in two weeks; on whole foods they lost the same. The driver was eating rate and energy density, not the ‘processing’ label — a follow-up showed a diet that was >80% ultra-processed but low in energy density still caused weight loss.

Energy density (calories per gram) is the master dial for how much you eat by volume. People eat a fairly constant weight of food, so water- and fiber-rich foods let you eat more while taking in less. In a year-long trial, the group told to add water-rich vegetables ate ~25% more food by weight and lost more weight. Evidence ●●●●○