If you exercise first you're more of what you just ate. Amino acids from protein is a source of raw materials. It also acts as a signalling molecule, triggering the growth of new muscle.

In healthy adults, about 0.25 grams of protein per kilogram of body weight is ideal for a given meal. That target can be hit three to five times a day. If you exercise before you eat, your muscles become more sensitive to protein's signals.

... you're less of what you just ate. Factors that make muscles less sensitive to protein signalling is ageing. Much of the muscle loss takes place during short periods of inactivity, such as bed rest after a knee replacement.

A simple fix is never to feed someone in a hospital bed unless absolutely necessary. Instead, get them up and make them shuffle to their food. The proportion of protein eaten should be higher to ensure sufficient muscle synthesis signals.

A study found that ground beef protein resulted in more tracer amino acid absorbed as well as it being absorbed more quickly. Another study showed that people who retained more of their own teeth tended to have more muscle.

Eating lying down will slow down protein digestion and possibly reduce the synthesis of new muscle protein.