Multiple good studies agree. Treat as settled.
A 2003 meta-analysis examined 250 supplements; only six had enough studies to analyse and only two worked. Creatine was one. Modern trials put it at about 2.5 lb of extra lean mass in under-50s — and 3 lb in older adults.
In men with obesity, losing weight by diet raised total testosterone about 72 ng/dL on average across 19 studies, and bariatric surgery about 208 across 26. Vitamin D did nothing in the trials. The famous sleep-deprivation figure rests on ten men and a p-value of .049.
Eggs raise LDL by about 5 to 8 mg/dL in the pooled trials, so "eggs don't affect your cholesterol" is wrong. Whether that matters for the heart is disputed: in six US cohorts the egg's link with heart disease followed the cholesterol in its yolk, and the big pooled analyses disagree. And two meta-analyses disagree about the one thing the "it's a wash" argument needs.
On an ordinary diet your muscle creatine is already 60–80% saturated, and supplementing fills the rest. Which is why, in one biopsy study given the same dose per kilogram, the group that gained most gained nearly six times the group that gained least — they started with the most room. Loading only changes how fast you arrive.
Pooled across 143 randomised trials: body mass up 1.9 lb on average, fat-free mass up 1.8 lb, fat mass unchanged, body fat percentage down. Skipping the loading phase does not skip the weight: trials that never loaded gained as much.
Canning doesn't destroy the omega-3s — canned pink salmon carries more than a gram per 100 g. But albacore packed in oil holds 0.24 g against 0.86 g for the same fish in water, because the fat dissolves into the oil and the oil goes down the sink. Figures pulled from USDA FoodData Central, with the FDA/EPA mercury lists alongside.
54 randomised trials, resistance training against people doing no exercise at all, nobody dieting: body fat percentage fell 1.46 points (1.08 in the trials that used DXA scans) and fat mass about 1.2 lb. The percentage moved further than the fat did, probably because muscle was going on, and a bathroom scale adds the two together.
By volume, yes — that is chemistry. But in a 12-week trial people gained about 2.6 lb of lean mass while losing up to 7 lb of fat, so their weight went down, not flat. And the density constant everyone quotes was measured in rabbits and dogs.
116 trials and 6,880 people say aerobic exercise works: about 2.8 kg at the recommended dose. The 'fat burning zone' printed on the machine is a different matter — and it's set at the wrong heart rate even by its own physiology.