Understanding the relationship between genes and bodyweight is key.
When I was a young postdoctoral researcher here at Cambridge in 2002, a senior colleague of mine took me to a fancy dinner at Peterhouse College, the oldest of the Cambridge colleges at more than 800 years old.
It was a multi-course affair, and rather ridiculously, you had to change seats (and hence dinner companions) for each new course. Given there were six courses, that was a lot of shuffling about.
At the beginning of the evening, just as we started the first course, an older bearded professor of something or other opposite me asked, ‘So young man, what do you do?’
I told him I was working on the genetics of childhood obesity, which elicited a surprising response.
‘Ha! Do you know what your problem is?’ he said jabbing his finger at me aggressively, ‘You give fat people an excuse.’
The disgust in his tone threw me, and as I mobilised all my diplomatic nous to gently push back, my evening was saved by a literal bell, letting us know to switch seats for course number two.
As I was heading home that evening, it occurred to me that, unpleasant though it was, the view of that professor was shared by a large proportion of society. The issue is that obesity is seen as a problem of physics. People just need to be more disciplined to eat less and move more.
However, while how we get to our bodyweight is reliant on physics, the relevant question is why? Why do people behave so very differently toward food? Why do some people respond to stress by eating more and others by eating less? Why do some people love food (like me), while others consider it a fuel?
Clearly why, how much, what, and when we eat, have powerful societal and cultural underpinnings. But there are equally powerful biological and genetic factors that influence our eating behaviour, and hence our bodyweight.
Read more about genetics:
- What actually is DNA?
- A neuroscientist explains how your genes affect your mental health
- Chris Hemsworth took a genetic test to screen for future health risks. Should you get one too?
How your genetics could determine your weight
The study of large population-based studies such as UK Biobank, a survey of nearly half a million volunteers from the UK, has helped to reveal the genetic architecture underlying differences in body size.
For instance, we now know of over a thousand genes that are linked to bodyweight, and the vast majority are expressed in the brain and influence our eating habits.
What is intriguing is that while there are overlapping genes, there are unique genetic signatures linked to developing obesity in childhood versus gaining excess fat as an adult.
Given that UK Biobank is a survey taken across the population at a single point in time, with all participants recruited as adults, the childhood obesity data was obtained by asking all the participants:
‘When you were 10 years old, compared to average, would you describe yourself as thinner, plumper, or about average?’
This clearly relies on childhood memories, but most people do recall their body size as children, and studies have shown a strong genetic relationship with measured childhood weight.
It is, however, still a blunt measure, and crucially, misses out on measures such as rate of growth, as well as contemporaneous information about illness, or types of diet.
There are ‘smaller’ studies available, such as the 12,000 participants of the Bristol-based Children of the 90s study, which provide rich and invaluable data. However, large samples on the scale of Biobank focussed on children, that are required for the study of more nuanced characteristics, do not exist.
What data is needed to beat childhood obesity
Obesity is one of the leading public health problems we face today, and we know that children with obesity overwhelmingly grow into adults with obesity. Thus, understanding the genetics and natural history of childhood obesity will play a crucial role in its treatment and prevention.
D-CYPHR is a genetics health research programme led by the National Institute for Health and Care Research (NIHR) BioResource, that is uniquely open to every child in the UK.
Its ambition is to be truly inclusive, with recruitment open online to all 14 million children in the UK – any family can join. It will investigate a wide range of conditions, from mental health to cardiovascular disease and diabetes, for which growing rates of obesity are a major contributing factor.
Inclusivity here really does matter, because to date, more than 80 per cent of human genetic data worldwide comes from people of white Northern European descent. This means much of our understanding of human traits and disease is currently limited by this skewed perspective.
People of different ethnicities have different risk profiles for various diseases, and understanding these improves our ability to treat and prevent disease in everyone.
This UK government-funded project plans to limit location-based biases by recruiting children online, encouraging families to join from home and providing them with a kit to return a saliva sample.
D-CYPHR is ambitious and will face challenges in creating a truly inclusive research sample. However, if this programme does indeed live up to its promise, it would circumvent many of the problems in adult health research, building diversity right from the beginning.
For the first time we could track the bodyweight and health of an ethnically and geographically representative group throughout life, revealing how different environments interacts with genetics to impact the development of obesity.
Improving the health of children, all children, must be a priority, if only because unhealthy children tend to become unhealthy adults.
Read more from Giles Yeo:
- Looking to lose weight? Here’s why exercise (probably) won’t work
- The paleo diet is a ‘Flintstone fantasy’. A scientist explains why
- Is BMI a useful measure of a healthy weight?