More or bigger fat cells?
When adults overeat, the fat cells in their waist expand, while the fat cells in their thighs grow in number, at least in the short run. Earlier studies had suggested that adults don't grow new fat cells.
Researchers at the Mayo Clinic told 28 normal-weight men and women (they were roughly 30 years old) to eat until they were more full than usual at every meal, and to also eat one to four daily "supplements" (a king-size Snickers bar, a Boost Plus "nutritional energy drink," or an ice cream shake). Each had about 350 to 500 calories.
After eight weeks, the participants had gained about 10 pounds--including 8 1/2 pounds of fat. On average, subcutaneous (just-below-the-skin) fat cells in the belly got bigger, while fat cells in the thighs grew in number. The average participant created 2.6 billion new thigh fat cells.
Like it or not, thigh fat may be less damaging because belly fat is more closely linked to diabetes and heart disease. However, there were hints that "extensive, prolonged" weight gain would also lead to more belly fat cells. That's what happened to women whose belly fat cells were large when they entered the study. (Sorry. There's no easy way for you to tell how large your fat cells are.)
What to do: The next time you reach for more, don't forget: your body has to put the excess somewhere.
Proc. Natl. Acad. Sci. 107: 18226, 2010.