The obesity epidemic spans race, socioeconomic status, gender and nationality. It is a global problem and not restricted to one type of person.

Therefore it would be incorrect to suggest that obesity is caused solely by our genetic makeup.

However, there is research that indicates that our genes do play a role in our weight.

The UK’s Sharp Increase in Obesity

The number of obese people in the UK has been on the rise since the 1960s. Back then obesity prevalence was low at only two percent, whereas today it has risen to approximately 28 percent.

Changes in genetic make up take many years to manifest. Consequently such a rapid rise in obesity levels cannot be attributed to genetics alone.

Physical inactivity is on the increase as is the presence of calorie dense foods in our diets.

However, not every person who fails to live a suitably active lifestyle while following a healthy diet will become obese.

What makes some people more likely to be overweight than others?

If we look at body weight in the most simplest of terms, it can be said to be determined by a combination of the following aspects:

  • How many calories are consumed
  • How many of these calories are stored by the body
  • And how many of these calories are burnt off as fuel

All three factors can be influenced by our genes as well as our environment:

  Genes Environment
Calories consumed Appetite, satiety Access to food
Calories stored Body fat distribution Access to high density calorie food
Calories burnt off Metabolism, sedentary tendency Access to exercise

While genes may play a part in a person’s predisposition to how their body converts food to energy and distributes and stores fat, there are other environmental factors that must be taken into account.

Gene variants

Genome-wide studies have been continue to look for gene variants that can be attributed to a particular disease. Obesity is one such complex condition.

A minute change in the structure of DNA is referred to as a gene variant or single-nucleotide polymorphism and can be linked to disease prospects.

Obesity gene variants have been discovered in chromosomes 16 and 18. Carriers of the genes may have a 20-30 percent higher risk of being obese.

In the majority of cases weight control is not limited to one type of gene (monogenic). Instead it is influenced by a complex combination of genes (polygenic) and environmental factors.

What is the ‘Thrifty Gene’ hypothesis?

The thrifty gene hypothesis draws on evidence that our ancestors survived times of famine by evolving a gene which allowed the body to effectively store fat. The stored body fat was used to fuel the body until new food supplies were sourced. 

Those who were able to survive periods of food shortage passed their ‘thrifty’ gene down through the generations.

Obviously today we are not required to hunt and gather our food as in times gone by. Therefore the presence of this gene is rendered obsolete and yet its effects may still have a hold on how our bodies store fat.

What control do our genes have on our weight?

Over 400 genes are thought to play some part in weight control. The genetic regions that have been identified as contributing to body mass index (BMI) are made up of a broad cross section of the human genome.

We would expect to see gene variants falling into the areas that control appetite and the nervous system. However learning, memory and emotion have also been found to play a part

Our genetic makeup may hold some influence on the following:

  • Appetite levels
  • Metabolism
  • Satiety
  • Body fat distribution
  • Psychological reaction to food
  • Food cravings
  • Sedentary tendency

The influence that your genes have on weight can vary greatly from person to person. Research into the area has suggested that the range falls somewhere between 25-80 percent.

Is it possible to know if your genes are controlling your weight?

No. Unfortunately a definitive answer to this question would require expensive DNA profiling. However, there are a few identified factors that may provide you with a good indication:

  • You have one or more direct relative that is overweight. If both of your parents are overweight then your obesity risk factor can increase by up to 80 percent.
  • You struggle to lose weight.
  • You have been overweight for most of your life.

Those who closely fit the above criteria may find it more difficult to maintain a healthy weight. In these circumstances professional medical input may benefit the individual.

Whilst it is an easy assumption to make that obesity runs in families it is very rare that the condition is caused by one specific gene fault. Instead it is much more likely that multiple gene interactions, as well as environment, play a part. 

The future of genetics and obesity

Achieving a better understanding of the role that genes play in obesity is important in order to improve treatment and manage the epidemic.

The development of more effective therapeutic strategies will rely on increased knowledge of the underlying biology of the condition.

In the future weight loss strategies could be personalised to target the individual’s specific gene variant. This would provide them with the most effective means of reversing or avoiding obesity.

Obesity is not caused by one single factor. It is important to remember that the role of genetics in weight control is small and the predisposition towards weight gain due to genes does not mean that obesity is inevitable.

If you are looking to lose weight then a varied and balanced diet is usually the best starting point. However, if you encounter any considerable problems you should seek advice from your doctor. If your weight is posing a serious risk to your health, a doctor may suggest prescription weight loss medication in some cases, to be taken as part of a controlled programme of weight loss including regular exercise and a healthy diet.