Two factors contribute to an increase in fat mass: the number of fat cells and how much fat each of these cells stores (their volume). Spalding and colleagues studied the dynamics of fat-cell number in some 700 adults, both lean and obese, and combined their data with previous observations in children and adolescents.
Irrespective of weight, the number of fat cells seems to rise steadily from birth to the early twenties, but remains constant thereafter. In patients observed before and up to two years after surgical treatments that facilitate weight loss by reducing stomach size, no decrease in fat-cell numbers was detected, although their volume did drop.
Fat cells have a high turnover: new cells are continually being produced to replace their dead predecessors. The average age of a fat cell seems to be about 10 years in both lean and obese individuals, and the number of fat cells as a proportion of all cells remains constant in each weight group. But the total number of new fat cells was higher in obese subjects, suggesting that they are replenishing an existing larger pool.
In lean individuals the fewer fat cells can still store large amounts of fat
Fat people can still reduce the volume, it not the number of their fat cells.
Shadan (2008), What’s your fat allowance? Nature vol 453, p 169
(K.L. Spalding et al .( 2008 ) Nature vol 453 18th May .
- Martin Eastwood