“Over a 10-day hospital stay, a healthy adult can lose five percent of their total muscle mass. Those numbers rise to 18 percent in an intensive care unit... You can lose it so fast, but rebuilding it takes months... makes it harder to fight illness. A 10 percent loss leads to impaired immunity and increased risk of infection. Twenty percent means weakness and slowed healing; 30 percent leaves a patient too weak to sit. A loss of 40 percent is often fatal.” - https://m.medicalxpress.com/…/2020-01-nutrition-expert-musc…
How much lean tissue you have is tightly correlated with life expectancy, cancer survival, all illness recovery, and, obviously, overall quality of life. People fight tooth and nail to drop BMI, but some decreases in BMI increase risks.
The battle to keep muscle is very difficult. The ordeal to build more is unimaginable for most. Let us move the conversation away from simply dropping weight. Many people lose weight only to worsen their health prospects. Muscle mass can make the difference between life and death.