Scientists in the U.S. examined MRI scans of patients who chose various different methods to shed the pounds.
They discovered the brain reacts differently to images of food once the weight has been lost, depending on the method used.
The study, carried out at the University of Missouri-Kansas City, compared those who lost weight after bariatric surgery, and those who opted for more conventional dieting methods.
Following their weight loss, when confronted with images of pizza and other appetising food, scientists noticed the brains of the dieters were more active in the medical prefrontal cortex – the part of the brain known to regulate emotion and evaluate how we feel.
The new study suggests that food means more to those who lose weight by changing their behaviour – i.e. reducing the number of calories they take in every day, and by increasing the exercise levels.
On the other hand, people who undergo laparoscopic banding surgery appear to be more ‘disconnected’ from hunger pangs.
‘They’re not as interested in eating,’ said lead author Amanda Bruce, psychologist at the University of Missouri-Kansas City and the University of Kansas School of Medicine. ‘They’re not as motivated by food.’
The study, which was published in the journal Obesity, is the first to assess changes in the brain associated with different methods of weight loss.
Sixteen people who lost weight via dieting and 15 who had undergone bariatric surgery took part in the new research.
They were of similar age, education level, and importantly had similar BMI’s – body mass indices.
‘A huge strength of this paper is that the people in the two different groups were a match on the weight that they had lost,’ Ms Bruce said, reported futurity.org.
The results showed the bariatric participants lost about 9.3 per cent of their body weight, while their dieting peers shed 10.8 per cent.
Each participant was then given an MRI scan and scientists studied their brain activation levels as they looked at pictures of food.
They were tested before and after losing weight.
Dr Bruce said she expected to see differences between the groups’ brain activity, but the differences recorded were not those she had anticipated.
‘The brain area that showed greater change in activation for the diet participants is an area that is associated with attentional processing, salience, how much you value something,’ she said.
‘When people are working hard to lose weight, they’re still really focused in on food stimuli.
‘They’re thinking about food a lot. That’s one of the challenges. They’re often thinking about the foods they maybe shouldn’t eat. They’re still very motivated by these food stimuli. They’re focused on them.’
Meanwhile the bariatric surgery participants were not as bothered by food.
Their second set of scans, carried out after they lost weight, showed decreased activity in the medial prefrontal cortex.
The study notes that evidence ‘supports the notion that surgical weight loss patients undergo a ‘forced’ dietary restriction in avoiding discomfort that renders food cues to be less rewarding and less salient’.