It's OK to indulge once in a while, study suggests: The body adapts to occasional short-term overeating: Body focuses on removing glucose to preserve insulin sensitivity in short-term overeating bout -- ScienceDaily
Although the amount of visceral fat that surrounds internal organs increased substantially, short-term overeating did not have a significant effect on the men's weight or fat mass. In addition, fasting levels of blood sugar and C-peptide -- an amino acid the body releases in response to increased production of insulin -- did not change. This finding was surprising because fasting levels of endogenous glucose -- new glucose the body produces in addition to what it has already stored for future use -- increased during the short-term trial.
Chronic overeating increased the amount of total body fat and visceral fat as well as post-meal blood sugar and C-peptide levels. However, it did not alter fasting blood sugar levels, endogenous glucose production or the rate of glucose removal from the body (glucose disposal). This may be because the nutrient profile in the long-term trial was consistent with a typical diet and dietary fat percentages did not increase. Long-term overindulgence in fatty foods, instead of more nutritionally balanced foods, may be an important factor that causes rapid changes in blood sugar control.