The Kettle Journal
Plain-language notes on the published research behind training, food and recovery. Every number here is traced to the trial or meta-analysis it came from, and cited so you can check it yourself.
Three meta-analyses covering more than 9,000 participants converge on a useful ceiling somewhere between 1.3 and 1.6 g per kg of body mass per day. The more interesting result is how wide the uncertainty around that number really is — and how little the protein does without the training.
A 12-month randomised trial assigned 609 adults to a healthy low-carbohydrate or healthy low-fat diet, and tested whether genotype or insulin secretion predicted who would do better on which.
Almost everything we know about processed food is observational. One inpatient crossover study matched the meals for calories, sugar, fat, fibre and sodium, then let people eat as much as they wanted.
Time-restricted eating is among the most popular interventions in nutrition and, lately, among the most rigorously tested. Randomised trials have now separated the effect of the eating window from the effect of simply eating less.
Prospective cohorts following hundreds of thousands of adults have tracked muscle-strengthening activity against death from any cause. The shape of the curve is the surprising part.
Cardiorespiratory fitness is one of the strongest measured predictors of mortality we have. The training literature is far less settled on how best to raise it than the internet suggests.
Hypertrophy and strength are different adaptations and they do not respond to load the same way. Meta-analyses comparing light and heavy training separate the two cleanly.
Controlled laboratory studies have put people on identical calorie-restricted diets and varied only the hours of sleep. What changed was less how much weight came off than what kind of tissue it was.
The eight-glasses-a-day rule has a traceable and rather embarrassing origin. The performance literature on dehydration is more interesting, and more equivocal, than either camp tends to claim.
Creatine monohydrate is the most-studied supplement in sports nutrition, which makes it a useful case study in what a mature evidence base looks like — including the places where it stays silent.