"Why are thin people not fat?" was a Horizon documentary shown last night. It's available on iplayer (possibly only in the UK). The programme followed a small group of young, naturally thin adults who were monitored for weight, measurements, body fat percentages and so on while eating huge amounts of food and avoiding exercise over a few weeks.
From memory, the following points came up:
*Naturally thin people found it difficult to put on extra weight. Two people could not manage to eat all the extra food.
*One person put on extra muscle instead of extra fat and increased his metabolic rate.
*All the participants easily lost weight at the end of the study
Meanwhile, some other obesity research was looked at:
*A virus which causes chickens to gain weight is more common in fat people
*Once laid down, fat cells don't go
*Evolution has selected for a tendency to fatness
*Small children fall into two groups - those who continue to eat when full, and those who lose interest in food when full
*People seem to have a set weight point and adjust their diet and exercise naturally to maintain that weight.
*Fat people who lose weight, have an appetite for extra food.
There was more, but that's a quick sum up.
I was particularly interested in this story, because for most of my adult life I wasn't fat. I was naturally slim - not thin, but within a "healthy" BMI range. I seemed to be very much like the naturally thin people on the programme. I didn't have any desire to overeat. I lost interest in food after I was full. I was never overweight as a child.
Now my weight has changed, but I still behave much like a naturally slim person. I have a normal appetite. I don't overeat. My house is full of chocolate and other treats left over from Christmas but I only have the occasional piece now and then - not because I'm trying to resist but because I don't want it. So the puzzle is - why am I eating as I have done for all my adult life (apart from a few misguided attempts to diet), but steadily gaining weight?
The programme didn't give any explanations for somebody like me. (Unless you count the virus idea people seem to be pooh-poohing at the moment).