Fructose on the brain

Fructose is getting a lot of attention in the research lately and much of it is directed at the link between fructose and weight gain. You consume fructose in fruit but you also get it as an added sweetener in soft drinks and many processed foods. The problem with fructose seems to be that it is metabolised differently to glucose. Now a new study has shown that it also has a different effect on your brain, which could be a big part of why fructose makes people gain weight.

In the new study, adults with weight in the “normal” range were given fructose and glucose solutions. Then MRI scans were taken of their brains to see what activity took place. The aim was to see if there was any difference in how fructose and glucose affect your brain.

The analysis showed that glucose, but not fructose, resulted in significant reduction in blood flow in the hypothalamus, insula and striatum. This is important because these are all brain areas that regulate appetite, motivation and reward. As well as decreasing the motivation to eat, glucose also increased connections between the hypothalamic-striatal network and that increases feelings of satiety, or being full.

All of that means glucose signals your brain that you have had enough whereas fructose does not. The result of fructose consumption then is that you eat more than you need to, and that will lead to weight gain. All of these effects are probably linked to a reduced release of insulin in response to fructose compared to glucose.

This is bad news for you but good news for companies producing processed foods packed with fructose. You will want more of those, and it may be that fructose is partly fuelling the super-size phenomenon.

The good news for fruit fanciers, and the researchers acknowledge this, is that when your fructose comes in fruit the fibre and other nutrients present mitigate the effects of fructose. So you can have your fruit but forget your soft drinks, fast food and processed “treats” if you want to keep the weight off.