The advice comes at you from every direction — celebrity trainers, Instagram nutritionists, morning television segments — and most of it contradicts itself within a news cycle. Eat fat, avoid fat. Skip breakfast, never skip breakfast. The carbohydrate is the enemy; the carbohydrate is the foundation.

Cut through the noise and the fundamentals are less complicated than the diet industry needs them to be. The foods that keep the body lean and functional have been largely the same for generations: vegetables, particularly the dark leafy kind that contain iron and folate; lean proteins from fish, legumes, and poultry; whole grains that release energy gradually rather than spiking blood sugar; and fruits consumed in whole form rather than juiced, where the fiber that moderates sugar absorption has been removed.

The research on satiety is particularly useful for people trying to maintain a healthy weight. Foods high in protein and fiber produce a feeling of fullness that persists for hours, reducing the likelihood of snacking on calorie-dense foods with little nutritional value. A breakfast of eggs and vegetables, for instance, will hold most adults through to midday without the energy crash that follows a pastry or sweetened cereal.

Nuts occupy a fascinating nutritional position. Dense in calories, they were long treated with suspicion by calorie-counters. But studies consistently show that regular nut consumers maintain lower body weights than those who avoid them — an effect attributed to the satiety they produce and the way their calories are metabolized differently than equivalent calories from processed foods.

Water remains the most underrated weight-management tool available. Many people interpret early hunger signals that are actually thirst, consuming unnecessary calories when a glass of water would have resolved the craving entirely. Drinking a large glass before meals reliably reduces the quantity of food consumed at those meals. It costs nothing and requires no subscription.