The genetic basis of obesity

Obesity. It's a global epidemic that now kills more people than malnutrition. Physiologists work to unravel the causes of obesity and the genetic factors involved.

Produced by Orinoco Communications for The Physiological Society
Animation: Hayley Evenett
Illustration: Alex Scarfe
Sound Design/Music: Alexander Bradley
Narration: Elisa Canas
Director: Peter Barker

Scientific advisor: Jeffrey M Friedman
Producer at The Physiological Society: Rachel Wheeley

Transcript:

Sometimes it seems like everywhere we look we’re exposed to adverts about dieting, urging us to lose weight.

Globally, the diet industry rakes in over £150 billion a year, and that figure is rising fast.

But, at the same time, worldwide obesity levels are also growing, and that matters, because obesity now kills more people than malnutrition.

So, what’s going on? Why are self-control and dieting alone unable to stop the growing obesity epidemic?

Research by physiologists suggests there are important biological factors at play.
Namely, that some of us are simply more genetically predisposed to become obese than others.

The root causes of obesity can be summed up like this: food intake, minus energy burned, equals fat stored.

So, obesity occurs when we consume more than we burn, and fat mass builds up.

But what happens when genetics are thrown into the mix?

Our understanding of this field has been advanced by scientific experiments involving a species of obese mouse.

These mice are always hungry and won’t stop eating. They never feel full.

The mice weigh three times more than normal mice because of a defect in a single gene.

Scientists identified that gene as one that codes for a hormone called leptin.

Leptin is made by fat cells and signals to the brain how much fat mass is in the body.

Without it, the brain mistakenly believes the body is starving, so the mice keep eating, even though they’ve had enough food.

Scientists translated this finding to humans when a four-year-old boy with the same genetic mutation became severely obese.

With regular leptin injections, his over-eating stopped and, by the age of eight, he was no longer overweight.

Studies of twins have helped us to identify the genetic basis of obesity.

Identical twins who come from the same egg and the same DNA have very similar body sizes.

But twins that come from different eggs show much more variability.

These studies show that while single genes are occasionally responsible most obesity cases are caused by a combination of genes working together.

Understanding the causes of obesity is far from simple but genetic factors such as leptin play an important role to regulate food intake and body weight.

So self-control alone is rarely enough to overcome the powerful effect of genes.

That’s why physiologists are working hard to assess how a healthy diet and exercise, combined with a better understanding of how genes influence obesity, can help turn the tide on this global epidemic.

[Asus_sugoma]

The video didn't claim that obesity could be explained by genetics, it claimed that genetics is *a factor* that influences hunger and therefore influences food intake and therefore can indirectly lead to obesity when there are enough calories available.
It did not claim that the increase in obesity was due genetic mutations, but explained that genetics is *one* of the factors that can contribute to obesity.

[GoodDr.]

We need policies that support healthy living, from schools to workplaces to communities

[mattias]

What prevalence does this mutation have?

[kezmenflowers]

Ive always struggled with obesity ever since i was a kid because i was more susceptible to it than the rest of my family and yet im more active and have done way much more than my family has. There can be genetic differences even though you do come from the same family. I also come from parents that were addicts also, so i had to overcome drug and alcohol addiction and just got rid of eating highly processed sweets. So i dont want to hear people say its because im lazy because i am very active and do move a lot but yet i see people who are chain smokers and alcoholics who are based on society standards healthy looking and yet i dont drink nor do drugs but just because im overweight i get harshly judged and devalued because of how i look. F you society.

[saulwilliams-wilson]

but obesity is a relatively new phenomena. have our genes changed so fast?

[WorthlessWinner]

Not sure if the focus on leptin is appropriate as, even with the "rarely due to a single gene" disclaimer, it can perpetuate the myth that something has to be Mendelian to be 'genetic'

[henrybird]

I think when you focus and blame, obesity on one characteristic, such as genetics You lose your objectivity, and as a result, you lose focus on the problem.

[adamwilliams]

I don't buy into people carrying weight in all instances because they hide calories or don't train. I have a careful balanced diet and I train sometimes twice a day but everyday. Sometimes 2 or 3 hiit or bootcamps in a day. 3 dog walks and play football as well as swim 60 lengths a few times a week. I have belly fat I can't shift. My parents both had the same issue. My calorie intake is around 2500 because I train a lot. When I lower it I'm tired and can't train as hard. But it's annoying

[rohinisivamurthy]

This is confusing. I have come across people who eat more than an over weight person and does no exercises yet still stay thin. I feel some kind of metabolic gene or a fat burning gene in them keeps burning all the fat 24/7 no matter how much they eat.

[truesheltopusik]

"self control alone can not overcome the effects of genes"

Bro the case you talked about was how certain genes can make you want to eat more, that is exactly the kind of thing that can be overcame by having more self control.

[nealwright]

Watch videos of the sixties and earlier and then rethink this.

[leoalphaproductions]

I’m pretty sure I have obesity issues. I gain weight rapidly if I’m not working out or on a proper diet. Also I have issues where I’m always hungry if I’m not eating the right food.

I cut out carbs and sugars 2 years ago, and now all I eat is meat. The fat practically melted away within months and I wasn’t even that active. Now I have an average BMI and I’m healthier than most people. Also didn’t have any hunger issues either. I think those carbs and sugars have some real physiological effect that just keeps you hungry and fat.

[the_truthdealwithit]

Bull!!! Have some self control and eat healthy and exercise. Obesity is not a disease, its a lack of self control & self pride! Make living healthy a lifestyle and stop making excuses!!!!

[MrBeard-igzc]

Nobody was far 100 years ago. It's not genetic.

[julianbatiste]

When around my father I just want to give up at life and just die, he has never worked a day in his life, he a crack head/drug head, he very unhealthy, he never supported me, he blames his problems on everyone else, he has full common sense but refuses to use the brain god gave him, he calls everyone the devil who’s doing better then him, he says in order to be successful you have to give your soul to satan, hes a leach, he’s 50 and still lives with his mother but his father was a very successful man (he was a boss and owned business) my father has more then a hundred lazy bones in his body, I’m 20 Nd black of color what I inherited from him walking into man hood was bad hygiene, bad health, I never peaked, missing teeth, doubt that I will be somebody and confusion on how to be a man / my mom is a hardworking mother and father and what I inherited from my mom was to never give up no matter how bad my situation is and a hardworking work ethic on the job and positive mindset off the job

[dlaregleyar]

"To lose weight, eat low carbs only. Avoid rice, sugar, pasta, soft drinks, and bread. Opt for avocado or berries as your fruit choices. For protein, consume any meat, eggs, chicken, or fish. Stick to leafy green vegetables for your vegetable intake. Additionally, include walking exercises and fasting to expedite weight loss. Consider drinking 1 liter of water with 1 teaspoon of salt as an electrolyte supplement. This will help maintain proper hydration and mineral balance in your body."

[kajal-jzbr]

Stholyantak Churna by Planet Ayurveda is a unique Ayurvedic herb that is effective in weight loss.

[GardensoftheAncientsHerbal]

So it’s not that genetics per se make you fat but influence your habits and impulse….

[Kevork]

Yeah maybe also mention the billions spent on advertising fast food?

[MaximDavinchki]

Back then in the 70s and 80s obesity wasn‘t as common as nowadays.