Fat provides 9 kcal per gram - more than twice the 4 kcal/g of protein or carbs. Daily fat target = (Daily calories × Fat percentage) / 9. For 2000 kcal/day with 30% from fat: 2000 × 0.30 / 9 = 67 g fat. For 2500 kcal/day at 25%: 69 g. For keto at 70% of 2000 kcal: 156 g. The percentage you choose depends on diet style: 20-25% (lower-fat, higher-carb), 25-35% (standard IOM range), 35-45% (Mediterranean), 60-75% (keto).
Minimum fat threshold for healthy adults: 0.5 g/kg body weight or 20% of calories, whichever is higher. Going below this for extended periods disrupts sex hormones (testosterone in men drops 10-30%; menstrual irregularity in women), reduces fat-soluble vitamin absorption, and degrades skin/hair quality. Sports nutrition research consistently supports keeping fat above this floor even during aggressive cuts.
Fat sources differ significantly in health impact. Monounsaturated (olive oil, avocado, nuts): consistently cardiovascular-protective. Polyunsaturated omega-3 (fatty fish, walnuts, flax): essential for brain and cardiovascular health, typically deficient in Indian diets. Polyunsaturated omega-6 (vegetable oils, processed foods): essential but usually overconsumed; excessive omega-6:omega-3 ratios may promote inflammation. Saturated (dairy fat, coconut, animal fat): mixed evidence - source matters more than total amount. Trans fats (industrial processing, hydrogenated oils): clearly harmful, eliminate entirely.