After eating the same meal, older people’s bodies release more insulin than younger people’s, which could mean their metabolism works differently as they age.

People with obesity tend to have higher insulin levels when fasting and their blood sugar spikes more after eating carbs, but their bodies still use the sugar from those carbs just like lean people do.

When people don't eat for 3 days, their insulin levels drop significantly, which is part of the body's adaptation to fasting.