How the brain controls what we eat

Why are some people severely obese? According to Dr Giles Yeo,  Director of Genomics/Transcriptomics in the Department of Clinical Biochemistry, it is all to do with the brain. “The more we find out about obesity the more we begin to realise that whenever you deal with obesity it invariably comes down to food intake and you invariably end up in the brain,” he says.

Dr Yeo will be presenting a BBC Horizon programme in June/July 2016 on the science of obesity and how biology dictates that some people just feel hungrier than others. It will cover the latest research in epigenetics, particularly drugs which change the gut hormone profile and trick the stomach into reacting as if it has had bariatric surgery without people having to actually go through it.

Dr Yeo’s own research investigates how the brain responds to circulating hormones which reflect the body's nutritional status. His ultimate goal is to devise treatments that work for all the different subsets of obese people. Currently, the only solutions are exercise and diet, for instance, eating food that takes longer to digest; bariatric surgery, which reduces stomach space and is major surgery, only appropriate for the most serious cases; and drugs that have side effects such as depression and high blood pressure, mainly because the brain is so complex and they are not targeting the right neurons.

The Horizon programme came about after Dr Yeo took part in a BBC three-part special on personalised dieting last year.  “The idea for the programme was whether by looking at a person’s biology we could tailor fit something that would work better than the standard diet,” he says. He participated in the programme in his capacity as a genetics expert and took part in the Cheltenham Science Festival as a result. There he took part in a Q & A about the programme. The editor of Horizon was in the audience.

Dr Yeo, who will also be delivering a talk about his research as part of the Cambridge Series at the Hay Festival on 4th June, believes it is important for scientists to engage with the public about what they are doing.  He says: “I know some people who think public engagement is of little value, but just a tiny fraction of the population will look at my research papers. I am paid by the Medical Research Council and 99.9% of people will not know about my research, but they are paying my salary. At a time of austerity people might ask why should my money go to researching obesity when there are other more immediate diseases. The common assumption is ‘don’t fat people just have to eat less’.”

They need to understand, he says, that the question is not about why some people get fat and others don’t. It is why some people eat more than others. "Obese people are judged all the time and portrayed as greedy, lazy and having a lack of willpower, but nothing is further from the truth. They are fighting a biology which means they are more hungry than other people. It is no challenge to stop eating when you are not very hungry. It is much harder when you are hungry. Obese people tend to feel hungrier all the time.” The environment we live in, where we are surrounded by cheap sugary, fatty fast food at all times doesn’t help, he adds, but the environment can be changed. People’s biology cannot.

Dr Yeo backs the sugar tax on fizzy drinks because of the way sugary drinks are absorbed quickly into the bloodstream, but he is against a general sugar tax, saying that scientists and health workers need to work with the food industry to promote change. “Sugar is not bad. It is the amount of sugar we eat that is bad,” he says.

He adds that just telling obese people that they are not bad, that they are just fighting their biology, can have a huge motivational impact. “Eating is a complex behaviour and like all complex behaviour it has biological underpinnings,” he says.