Low Blood Sugar Controls Appetite -- Not Genes

A key to effective diabetes management is keeping steady blood glucose levels. Steady blood glucose levels have many benefits, including the prevention of hypoglycemia. But there’s another potential key benefit that comes from keeping steady blood glucose levels: the prevention of overeating.

A new study lead by Dr Ellen Schur of the University of Washington looked at 21 pairs of identical twins in order to examine whether there were inherited traits in the way they responded to photos of food, and if that response changed when they were full.

The twins ate identical meals and had functional MRIs while looking at both high calorie and low calorie foods. The researchers were curious as to whether twins were more identical to each other in their responses to photos of foods than non-related individuals.

The conclusion was that genes and upbringing (how our family behaved around food) have little influence on our brain appetite centers – even after a few hours without food. Instead, activation in our brain appetite centers was strongly related to our blood glucose levels.  People who had lower blood glucose levels responded strongly to pictures of calorie-dense, fattening foods.

Fullness However, Runs in the Family…

Although appetite might be driven by our blood glucose levels, satiety tends to be influenced by genetics and upbringing.

The twins in this study were later fed macaroni and cheese for lunch, given another MRI exam, and then shown more photos of food.  Researchers found that each pair of twins was more similar to each other in how their brain appetite centers were activated, but that twins who still had low blood glucose levels, had more brain activation.  When these twins were let loose on a buffet, they ate similar amounts and reported similar levels of fullness – indicating that genetics and family influence might play a role.

So, these twins, although they had different appetite levels and signals, kept eating anyway – perhaps out of family tradition and some genetic role. Could not letting ourselves get very hungry (or with low blood glucose) be a key in helping curb how much we’ve been raised to eat?

Dr Zane Andrews, of Monash University, comments that “If the brain senses that blood glucose is getting low it will do all it can to get you to eat.” Any one of us who has experienced low blood glucose (or hypoglycemia) knows that one of its red flags is intense appetite, or hunger – and that, as blood glucose levels normalize, it can be very hard to stop oneself from overeating.

Researchers suspect that this desire to keep eating could be the reward pathway. It’s a pathway that gets activated when a person does drugs like cocaine… or when they eat. No wonder it’s so challenging to not overeat! This means that things like skipping meals are NOT a good idea as they will keep feeding into this starvation and reward mechanism.

Perhaps future studies will tell us how obesity may affect these appetite centers.