Estimates for the total decline in the muscle mass between the ages of 40 and 80 years range from 30% to 50% and the annual decline in functional capacity is around 1–2% after the age of 50 increasing to as much as 3% after the age of 60.
Food products that can delay/reduce this problem will be big business. That is a certainty.
Something that will be of major importance to all marketers is the impact of muscle loss on the factors that determine the customer experience. Kim Walker and I wrote about this in Marketing to the Ageing Consumer. If you want to read the gory details then have a look at this academic paper. Dick Stroud