Alcohol, For sure is one of them, Pesticides, Household products, Etcetera..
Answer:
your health
Explanation:
if you are a diabetic, you need foods with no sugar or sugar substitutes
The least likely explanation for this would be that they're training at different intervals, or one is training harder than the other.
The most likely reason is that the way the other person's genetics are most people cant gain muscle as well as others because of disease or their body structure.
Hope this helped!
Probably spreading depends on the context you probably should add