What is in control of your appetite?

With democracy and affluence comes overweight, poor food choices and laziness. OK, not laziness, just the decision to remain on one’s bottom for hours and hours. Why don’t people in well-off countries eat more healthy and get out and boogie? Find a solution to that and you can write your own ticket.

Genes meet environment

A bunch of European scientists believe that part of the problem is that some nutrition decisions are genetically determined and very difficult to change. It seems that the environment doesn’t change your genes, but it does determine which genes are turned on and off.

Having abundant food around increases the individual limit for food to be satisfying. One paper showed that changing to a healthier diet for a few weeks modulated the response to over 500 genes. In other words, gene expression returned to normal. Sadly, the environment tends to over-ride this for many as we are surrounded with eat-me, buy-me cues, returning gene expression to over-eating.

Time of the season

Animals that experience seasonal or daily variation in food availability (think of hibernating or hunting animals) tend to eat more than is necessary when they find food. They store the excess food as body fat, which is then used during times of food shortage. When these animals experience long-term abundance they over-eat. Humans are one of these animals. In affluent democracies not only are half of the humans overweight, half of the cats and dogs are too.

It’s not just humans that prefer processed and cooked food, the great apes are a big fan as well. Many other wild animals prefer cooked food to raw. Choosing foods that are rich in kilojoules means that an animal will grow faster, reach reproductive age quicker, protecting the survival of the species. The authors argue that this hard-wiring to eat, grow and reproduce is one reason we choose cooked and processed high kilojoule/calorie foods over minimally processed foods.

Gene defect

There are the unfortunate who have a specific genetic defect that drives them to eat too much, such as Prader-Willi syndrome. I used to look after kids with this syndrome when I worked at the Children’s Hospital in Sydney deep in the last century. By default, I became the Australian expert on PWS and spoke at conferences. It’s tough for parents when you have to lock all food cupboards and the fridge because your child’s appetite has no off switch. Ever.

What does it all mean?

Now, I can’t say I fully understood this paper, but the jist seems to be that we are similar to other animals in that we are genetically geared towards over-eating as that makes us more likely to survive famines, live to maturity and reproduce. Go to the paper if “epigenetic mechanism of methyl–cystine bonding” in gene expression sparkles your mind.

It also means, and this bit is worrying me, that if you have children and have now brought them up to a reproductive age, then you are no longer required by nature. Watch your back.

Reference: Appetite. 2010; 54: 442-449