Body weight changes when energy in exceeds energy out over time. Carbohydrate and protein each provide about 4 kcal per gram, fat provides about 9, and alcohol provides 7 with no nutritional contribution. Fiber is counted at roughly 2 kcal per gram because it is only partly fermented in the gut.
Why two same-calorie foods differ
A 200 kcal serving of chicken and vegetables and a 200 kcal serving of soda deliver identical energy but diverge on protein, fiber, satiety, and micronutrients. Satiety matters because it determines how much you eat at the next meal — the downstream effect that calorie figures alone never capture.
Where the database's calorie leaders sit
The top of our energy ranking is oils, butter, nuts, chocolate, and dried goods — foods that are low in water and high in fat. At the other end, water-rich vegetables and fruits sit below 50 kcal per 100 g. Neither end is inherently good or bad; both are facts about water and fat content.
Practical tracking
Accurate tracking needs portion weights, not guesses: cooking concentrates or dilutes foods differently than packaging implies. Weighing food for a week teaches more about real intake than a month of estimating by eye, after which visual estimation usually becomes reliable enough.
Energy needs vary
Basal metabolic rate depends on body composition, age, sex, and thyroid function; activity then adds the variable part. Formulas give population estimates, not your number. The reliable method is tracking intake and body-weight trend together for two to three weeks and adjusting from observed results.