Why are we getting so fat?
Author: Professor Joyce Harper
In the UK, the BBC Horizon series recently showed a programme presented by Dr Giles Yeo, a geneticist from Cambridge University, giving an update of research into obesity – why are we getting so fat?
Key facts from the World Health Organisation
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- Worldwide obesity has more than doubled since 1980.
- In 2014, more than 1.9 billion adults, 18 years and older, were overweight. Of these over 600 million were obese.
- 39% of adults aged 18 years and over were overweight in 2014, and 13% were obese.
- Most of the world’s population live in countries where overweight and obesity kills more people than underweight.
- 42 million children under the age of 5 were overweight or obese in 2013.
- Obesity is preventable.
Professor Keith Godfrey has been looking into genes which are switched on and off in the womb and has shown that these can have a long term effect on the child. High sugar levels in pregnancy can cause more fat cells to be made in the fetus.
There are many studies looking at genes that predispose people to being obese. The main gene is called FTO – fat mass and obesity-associated gene. This gene changes the way our brain thinks about food – it works by letting the brain think we are thinner than we are, causes craving for sugar rich foods and makes us think we are eating less than we actually are. It is related to how the reward pathways work in the brain. People have a different versions of the gene. Those with two at-risk copies of the FTO gene – called a double variant – are 70% more likely to be obese but the good news is that they are also more likely to lose weight through exercise. Those with one at-risk copy are also more likely to be obese.
Obesity surgery in the UK costs the National Health Service £85 million per year. The only surgery proven for weight loss is bariatric surgery which reduces the stomach size from 900mm to 30mm. This is normally done by inserting a gastric band or performing a gastric bypass. But it has huge risks and is very expensive. Dr Steve Bloom and Tricia Tan from Imperial College, London are looking at a miracle injection which could have a similar effect to a gastric band. They are looking at a triple gut hormone infusion which reduces appetite and foot intake. At the moment the trial is pumping a steady stream of hormones into the gut and participants are eating 30% less than the controls. The infusion only lasts for one meal but they are hoping to develop an injection that will have a longer effect.
There is also a lot of work being done into gut bacteria. There have been studies looking at twins where one is a normal weight and one is obese. Scientists have transferred the poo from the twins into mice. Those mice infused with the poo from the fat twin, became fat but there was no such effect with the poo from the thin twin. The theory is the gut bacteria in the poo are having an effect on the mice; these bacteria may influence the hormone levels in the gut. In the USA this study is being tested on humans. Poo from lean donors, which is thought to contain ‘good’ gut bacteria, are being transplanted into the gut of obese people. One hunger hormone, Glucagon-like peptide-1 (GLP-1)- rises after the transplants. Other scientists are trying to isolate the individual bacteria.
Professor Tim Spector from St Thomas’s Hospital, London and author of The Diet Myth; the real science behind what we eat, is looking at twins and investigating gut bacteria. He has found that high levels of one particular gut bacteria, the person will rarely get fat. He is looking at ways we can increase levels of this gut bacteria. He suggests we eat a high fibre diet with a lot of fresh fruit and vegetables.
So it looks like a combination of our genes, hormones and gut bacteria can effect our weight.
Read More:
http://www.bbc.co.uk/iplayer/episode/b07fys2y/horizon-20152016-11-why-are-we-getting-so-fat
Image credit: www.mirror.co.uk
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