As doctors, we are rarely taught this. We learn about body composition, metabolism, physiology, anatomy etc. But how much, when and why is sometimes more of the mystery. Or maybe I have forgotten all this.

Luc van Loon is a professor of exercise physiology and nutrition in the Netherlands and he has done amazing research in this field.  Most of the data written in this blog is from his research.

Can anyone put muscle on?

Yes, everyone can put muscle on, even elderly. In 2012 Luc van Loon published a study which has shown that even frail elderly can gain muscle mass during prolonged resistance-type training only if they supplemented their diet with protein shakes. Those elderly who did not supplement their diet with protein shakes did not increase their muscle mass during the same exercise regimen. This increase in muscle weight was 1.3kg in 6 months. They all exercised twice per week (resistance/weights exercises). These elderly were around 78 years old. There are many studies which show that younger adults can put muscle mass on with resistance exercising.

​Can anyone lose muscle mass?

Yes, especially the elderly. In another study, in just 1 week of bed rest, the elderly lose more, approx 1.4kg of muscle mass. This is a significant muscle mass loss.

All adults lose muscle after a period of inactivity, like being in plaster. I know that this has definitely happened to me after I broke my arm. People can lose 20-30% of their muscle mass during their hospital stay. And sometimes it is impossible to regain that muscle mass completely, especially in the elderly.
And how does this affect us all, especially elderly, who are in hospital more often and for a more prolonged time? Probably a lot. Elderly often have more reduced mobility at the best of times, and this definitely gets worse after muscle loss. So their mobility gets worse, they are than more prone to falls and return back to the hospital for more muscle loss.

What happens with the protein you eat?

Luc van Loon has shown that 50% of the protein that is consumed is absorbed into the circulation within 5 hours of being consumed. During these 5 hours, 11% of the consumed protein was incorporated into new muscle. He concluded that we humans rebuild 1-2% of our muscles every day, and all muscles are rebuilt within 2-3 months.

How much protein do you need to eat?

Adults need 0.25g of protein per kg of their body weight per meal to maximise protein synthesis signal, but elderly need 0.4g of protein per kg per meal.
If you eat protein before going to bed, you also boost your protein synthesis.
And exercising before eating will boost even more your protein synthesis signals.

What should we do in hospitals to prevent this?

We should mobilise people before giving them their meals and minimise the time they spend in the bed rest. The number of physiotherapists in hospitals is decreasing, but employing more would mean that people would mobilise more before eating, and having better mobility when they get home.
Also, we should bring back communal eating places, so people are encouraged to walk there to have their meals, instead than giving them meals in the bed (which is soooo much easier).