Protein Facts

Sedentary adults need at least 0.8 g of protein per kg of body weight per day (the RDA). Active adults benefit from 1.2–1.6 g/kg, and people focused on muscle growth or fat loss while preserving lean mass should aim for 1.6–2.2 g/kg. For a 70 kg (155 lb) adult, that is roughly 56 g (RDA), 84–112 g (active), or 112–154 g (muscle-building) per day.

Aim for about 0.4 g of protein per kg of body weight per meal, split across 4 meals. That works out to roughly 28 g per meal for a 70 kg (155 lb) adult, 32 g for an 80 kg (176 lb) adult, and 36 g for a 90 kg (198 lb) adult. Most people maximize muscle protein synthesis in the 20–40 g per-meal range.

Whey is a fast-digesting dairy protein (absorbed in about 1–2 hours) that produces a rapid spike in blood amino acids and muscle protein synthesis, making it useful post-workout and with meals. Casein digests slowly over 6–8 hours, producing a sustained low amino-acid release, which is why it is often used before long gaps without food (e.g., bedtime). Both are complete proteins derived from milk; most research shows similar 24-hour outcomes when total daily protein is matched.

No — the body does not stop absorbing protein after 30 g per meal. Essentially all dietary protein is digested and absorbed regardless of dose; large meals simply digest more slowly. The 30 g figure comes from muscle-protein-synthesis (MPS) studies showing that the MPS response plateaus at roughly 0.4 g/kg per meal (often ~30 g for younger adults). Excess protein is still used for other amino-acid-dependent processes, not "wasted."

A complete protein contains all nine essential amino acids in the amounts the human body needs. Animal proteins (meat, fish, eggs, dairy), soy, quinoa, and buckwheat are complete. Most single-source plant proteins (rice, beans, wheat, nuts) are incomplete because they are low in one or two essential amino acids — but eating a variety of plant foods across the day easily provides the full set.

For weight loss, the best proteins are lean, high-satiety sources: Greek yogurt, cottage cheese, whey, egg whites, white fish, chicken breast, and lean cuts of beef or pork. They deliver a lot of protein per calorie, which helps you preserve muscle and stay full in a deficit. Target 1.6–2.4 g of protein per kg body weight per day while cutting calories.

Timing matters a little; total daily protein matters much more. The post-workout "anabolic window" is roughly 4–6 hours wide, not 30 minutes. As long as you hit your daily protein target spread across 3–5 meals of 0.25–0.4 g/kg each, the exact minute you eat relative to training rarely changes long-term results.

Adults aged 65 and older benefit from 1.0–1.2 g of protein per kg body weight per day — higher than the 0.8 g/kg adult RDA — to offset sarcopenia (age-related muscle loss). Per-meal protein should be roughly 0.4 g/kg because older tissue is less responsive to protein ("anabolic resistance"). For a 70 kg senior, that is about 70–84 g per day in meals of ~28 g each.

For adults with normal kidney function, higher protein intakes — up to about 2.2 g per kg body weight per day — do not harm kidney health in the available evidence. People with pre-existing chronic kidney disease (CKD) are a separate case and should follow protein targets set by their physician or renal dietitian, typically lower than the general population.

Protein shakes usually deliver more grams of protein per calorie (often 20–30 g protein in 120–160 kcal), digest quickly, and have fewer added sugars than most bars. Protein bars are more portable, slower to digest, and better for satiety, but many contain added sugar, sugar alcohols, or extra fat that widen the calorie-per-gram ratio. Use shakes when you want efficient protein; use bars when you need a travel-friendly meal replacement.