Your health baseline in 5 steps

BMI gives you a quick screening number. It's imperfect -- muscle vs fat distribution isn't captured -- but it's a standard reference point for conversations with a doctor.

Your Basal Metabolic Rate is the number of calories your body burns at complete rest. Everything else -- deficit, surplus, weight targets -- is calculated as an offset from this baseline.

Whether your goal is to lose, gain, or maintain, your calorie target is just your TDEE (BMR × activity multiplier) adjusted by a daily offset. A 500 kcal/day deficit typically produces around 0.5 kg of loss per week.

Protein is the macronutrient most people underestimate. For active individuals, current evidence supports 1.6-2.2g per kg of bodyweight per day to preserve or build muscle.

Hydration needs vary by weight, activity level, and climate. The 8-glasses-a-day rule is a rough average; your actual number may be higher.