Exercise May Encourage Healthy Eating Via Brain Changes

Exercise may encourage healthy eating by changing parts of the brain that influence impulsive behaviour, according to a new review of the available literature by researchers from Spain and the US published in Obesity Reviews. The researchers conclude that in a society where we are surrounded by temptations and triggers that facilitate over-eating and excess, the part of the brain responsible for "inhibitory control" undergoes "relentless strain" (they note it has limited capacity anyway), and doing exercise on a regular basis enhances it.

"By enhancing the resources that facilitate 'top-down' inhibitory control, increased physical activity may help compensate and suppress the hedonic drive to over-eat," they write.

Obesity has been rising at an alarming rate in Spain in recent years, so much so that in some parts of Spain, the proportion of the population that is obese is higher than that in many parts of the United States, the country traditionally considered as having the highest obesity rates in the western world.

Also, in line with other countries in the Mediterranean, Spain has one of the highest rates of childhood obesity in Europe.

Co-author Dr Miguel Alonso Alonso, a Spanish neurologist working at the Harvard-affiliated Beth Israel Deaconess Medical Center in the US, told the press on Wednesday that many studies suggest "physical exercise seems to encourage a healthy diet. In fact, when exercise is added to a weight-loss diet, treatment of obesity is more successful and the diet is adhered to in the long run".

However, in order better to inform and improve current approaches and treatments for obesity, he and his co-authors, from the US and Spain, thought it might be useful to bring together what these "somewhat disparate, yet interrelated lines of literature" may have to say about the neurological underpinning of the link between exercise and weight loss.

"Designing effective weight-loss interventions requires an understanding of how these behaviours are elicited, how they relate to each other and whether they are supported by common neurocognitive mechanisms," they write.

There is evidence that regular physical exercise changes the working and structure of the brain. From their review, the researchers conclude these changes seem to support the idea that regular exercise improves the results of tests that measure the state of the brain's executive functions, and increases in connections in the grey matter and prefrontal cortex.

One of the brain's executive functions is "inhibitory control" which helps us keep check on impulsiveness, or to suppress inadequate, excessive or inappropriate behaviour toward a goal.

The researchers conclude that regular practice of physical exercise, in time, produces a "potentiating effect" on the brain's executive functions, including the ability for inhibitory control, and this helps us "resist the many temptations that we are faced with everyday in a society where food, especially hypercaloric food, is more and more omnipresent".

Exercise also brings other benefits, such as making the brain more sensitive to physiological signs of fulness. This helps not only to control appetite, but it also modifies the "hedonic" response to food stimuli, say the researchers. Thus the benefits of exercise occur in the short term (these affect metabolism) and in the long term (these affect behaviour).

Alonso Alonso and colleagues suggest it is important that social policies help and encourage people to practise sport and engage in physical exercise, whether at school, in urban settings, or daily life, with the help of public transport, pedestrianized areas and sports centres.