Yes, obesity can be passed on genetically.
Recent research has shown that there are genes which increase the risk of obesity in children and adults. These genes are often inherited from one or both parents. There are many things people with these genes can do if they want to fight the genetic predisposition towards obesity such as eat healthy foods, exercise regularly etc.
What is the heritability of obesity?
The heritability of obesity is the proportion of phenotypic variance due to genetic factors.
Studies have shown that sibling-pairs where one is obese and one is not, the probability of a non-obese sibling being lean increases with age. This suggests that genes play a role in determining body weight but it’s not the only thing that matters.
Obesity is not always heritable.
There are multiple factors which influence an individual’s body weight. One non-genetic factor is the environment shared by two or more people, your immediate family members and close friends can also have a big effect on whether you become obese or not.
What are some genetic factors that can cause obesity in adults?
There are many genes associated with obesity but only a few have been found in large enough studies for scientists to be confident that they play a role in obesity. Genes within the FTO, MC4R, BDNF and NEGR1 are all related to obesity, although there are probably many more that have not yet been discovered.
The FTO gene is especially important for understanding how obesity is passed on genetically because 2% of Europeans carry a harmful variant in this gene. This means that if both parents carry a harmful variant in the FTO gene and their child has inherited this variant then they have an 80% chance of also inheriting it.
What are some genes that increase the risk of childhood obesity?
Children who become obese before they reach puberty, and those with a family history of obesity are at a much higher risk of developing obesity than children without these factors.
There are three gene regions that have been found to be associated with body mass index in children but they appear to act together. One of these is the FTO gene region which increases the risk of obesity by 0-80% depending on whether or not you inherited harmful variants from both parents.
Research has shown that the FTO gene (fat mass and obesity associated) is to blame for the tendency of some people to be obese. This research was carried out by scientists at King’s College London in collaboration with the University of Copenhagen. The team looked through the genomes (all genetic material) of 12,000 people and identified a gene called FTO, which they believe is responsible for a susceptibility to obesity.
In the research it was established that those who have this gene have a 70% greater chance of being obese than those without it. However, Professor Colin Palmer from Kings College London says “Our study has found strong evidence that an increase in weight of just over one kilo every year, means that the chances of obesity are 70% higher in those with this genetic variant than those without it.”
The FTO gene is significant because it secretes an enzyme, which predicts whether or not somebody is likely to become obese. This research could be very useful for parents who want to determine if their child is likely to be obese as a result of their environmental conditions.
These researchers hope that by the end of this decade they will have developed some sort of screening system where parents can test whether or not their children are at risk from obesity . This could help prevent them from becoming obese and developing associated conditions such as type 2 diabetes, heart disease and cancer.
Although the FTO gene has only just been found to be associated with obesity it is already being used by scientists around the world in their research. As well as looking for ways to prevent obesity, research has also shown that it could lead to new treatments for epilepsy and mental illnesses such as schizophrenia.
However, those who are obese should not use this research to comfort themselves, because although it may be true that this gene is likely to make them obese, it is possible for anybody to lose weight. Genetics do not play the only role in obesity.
How is obesity heritability calculated?
The heritability of obesity can be estimated by comparing the body mass index (BMI) of twins with that of biological siblings. The greater the difference in BMI between these two groups then the greater the genetic effect on obesity.
The prevalence of obesity in twins is no greater than in singleton individuals. The genetic influence on BMI can be estimated by comparing the body mass indices (BMI) of identical twins with that of fraternal twins. Identical twin pairs are 100% genetically identical, fraternal twin pairs share on average 50% of their segregating genes. If the heritability of BMI is 100% then identical twins will have twice the BMI of that in fraternal twin pairs.
One problem with this method is that it tends to overestimate heritability because shared environmental factors are not taken into account. Furthermore, the heritability of obesity is likely to be lower in children than adults.
Other methods used for estimating the heritability of obesity include adoption studies and genetic markers such as single nucleotide polymorphisms (SNPs). The major problem with these techniques is that they are time-consuming and expensive, as well as being difficult to generalize.
Genome wide association studies (GWAS) are a powerful tool for identifying genetic loci linked with diseases or disorders. In GWAS, hundreds of thousands of SNPs from across the entire genomes of multiple individuals are tested for correlation with a certain disease. For example, a GWAS may test hundreds of thousands of SNP’s from across the genome for association with BMI. If a SNP is found to be associated then it may indicate that obesity risk is increased by being in possession of this allele and that this allele acts as a marker for an obesity-related gene.
A study recently performed in Denmark  examined the link between genetic markers and BMI. The 400,000 SNP’s used in GWAS were selected from the gene chip that was designed for the International HapMap Project. In total, 41 different loci associated with measures of obesity were identified.
This study has provided evidence for a genetic component to BMI and therefore is in favour of there being a strong heritable factor in obesity. The 41 SNPs found in the GWAS suggest that there are at least 41 different regions of our genome which affect the heritability of obesity and so more than 41 genes may be involved in the development of obesity.
What can people do if they have a genetic predisposition towards obesity?
If you know that you have a greater risk of becoming obese due to your genetics then there are things you can do to reduce this risk such as eating healthy foods and exercising regularly. Genetics only accounts for a portion of the variation in obesity so the environmental factors that you can control are very important.
You can try and fight the predisposition and reduce the risk of obesity by maintaining a healthy lifestyle. However, what causes people to become obese cannot always be changed because it’s in their genes.
Also, the main cause of obesity isn’t necessarily so simple. For instance, some people might be genetically predisposed to put on weight but it doesn’t necessarily mean that they will.
It’s critical to remember that genetics only accounts for a small percentage of the variation in obesity, so the external factors that you can influence are equally crucial.
If you know that you have a greater risk of becoming obese due to your genetics then there are things you can do to reduce this risk such as eating healthy foods and improve your lifestyle.
Obesity is caused by an energy imbalance, when people eat more calories than they use up. Obesity has many causes including genetic, environmental and behavioural. There are different types of obesity which vary in their cause, for example those who become obese due to medical reasons or those that do it themselves.
It is estimated that around 20-30% of the variation in human weight can be accounted for by genetic factors. In other words, if you take two people with a similar build and energy requirements, the person whose parents were overweight has a higher risk of being overweight.
Obesity is a difficult topic to explore because it can be influenced by factors both inside and outside of our control. The heritability of obesity has been found in some studies to be as high as 90% while others have shown that the genetic influence on BMI ranges from 0-50%.
There are many methods for estimating the heritability of obesity but they all come with their drawbacks, highlighting how complex this issue really is. One way we may get closer to understanding more about why people become obese is through genome-wide association studies (GWAS).
These types of studies examine SNPs across an individual’s entire genome looking for associations between certain genes and diseases like obesity.
A recent study looked at 400,000 SNP’s taken from GWAS designed for the International HapMap Project and found that there were at least 41 different loci associated with measures of obesity. This implies that there could be at least 41 genes involved in causing obesity and so GWAS may help us to understand more about the heritability of this condition.