Perhaps one of the more controversial “theories” in the arena of obesity and weight management is that of the set point theory of weight gain, and perhaps it’s time this one was sorted out. The principle of “set point” states that we each have a preferred weight at which our bodies will under “normal” circumstances try to maintain. When weight fluctuates in adulthood it is invariably due to shifts in fat mass that are largely responsible - particularly where changes occur over prolonged periods (although skeletal muscle loss or gain is intrinsically linked to total mass) . Unlike lean mass (which is rigorously defended from shifts caused for instance by under-nutrition, external stress or disease and rapidly returns to a pre-determined level set within the DNA of each cell) fat mass is different, and changes are not robustly challenged, particularly in those people considered to be genetically susceptible to weight gain – termed “thrifty genotypes”.
Set point theory suggests that whilst fat cells (adipocytes) are happy to grow (hypertrophic adiposity) or to a lesser degree shrink, they generally wish to maintain a particular size and it is therefore the number of cells that is the critical factor. Continued overeating leads to fat cells becoming full and new ones being created (hyperplasic adiposity) and this then subsequently re-sets the set point in an upwards only direction. This has been termed the “irreversible ratcheting up of weight through life”. This in itself is controversial because there is evidence to show that under prolonged weight loss, fat cells start to die off through programmed cellular death (apoptosis). More research is needed on this phenomenon which is currently inconclusive.
The crux of all of this appears to be that if indeed there is a preferred weight, then the body needs the right environmental conditions to be able to achieve this - which begs the question - what are the right environmental conditions. It is argued that these are the conditions under which we have evolved, and as bizarre as it sounds proponents of this theory describe a normal environment as our ancient pre-modern diet (paleolithic diet) alongside a very active hunter, gatherer, scavenger lifestyle – there are no recorded cases of obesity in people today living “traditional lifestyles”.
Clearly returning to a cave like existance is not feasible, but the theory probably rightly states that preferred weight (with respect to fat cells) is only a weak system and can’t cope with the immense pressure exerted by our current obesogenic environments, and weight gain becomes inevitable. Add to this the fact that within our population there are an unknown percentage of people that are genetically susceptible to weight gain and the obesity crisis starts to become a good deal clearer.
I suppose what this means for most people is that the further away from a “normal environment” that we move (healthy eating and active lives) the more difficult it will be for your body to regulate the amount of on board energy that it stores in the form of adipose tissue, and irrespective of your genetics fat mass will continue to acrue as the body struggles to maintian energy balance.