“Inability to store fat safely increases diabetes risk,” BBC News reports.
Researchers have found links between genetic variations known to affect the storage of fat in the body and type 2 diabetes, as well as heart attacks and strokes.
People can store fat tissue in different ways, such as in their legs and arms. While this may be cosmetically unsightly, it is healthier than storing fat in the abdomen (known as visceral fat), especially around the liver and pancreas.
This type of distribution is associated with insulin resistance – where cells in the body fail to respond to the hormone insulin – and type 2 diabetes.
This difference in fat distribution could partly explain why not all obese people develop type 2 diabetes, and conversely why some people of normal weight develop type 2 diabetes.
The study was based on data on around 200,000 people from the UK and Europe.
In addition to the link between body fat distribution and insulin resistance, researchers also found variations in 53 genetic areas increased the risk of insulin resistance, which leads to type 2 diabetes.
Previously, only 10 genetic areas had been implicated. The greater number of these variations, the higher the risk.
Though the study found links between these genetic areas and fat distribution, this type of study cannot prove cause and effect.
But it may help target future prevention and treatment strategies, such as medications designed to target the fat.
In the meantime, you can still reduce your risk of developing type 2 diabetes by making lifestyle choices like eating a healthy, balanced diet, stopping smoking, reducing how much alcohol you drink, and exercising regularly.
Where did the story come from?
The study was carried out by researchers from the University of Cambridge, the Wellcome Trust Sanger Institute, the University of Oxford, the University of Exeter, the University of Geneva, the University of California, and the National Heart, Lung and Blood Institute in the US.
It was published in the peer-reviewed journal, Nature Genetics and was funded by the UK Medical Research Council. The authors declare no competing financial interests.
BBC News reported the story accurately, linking the inability to store fat safely to an increased risk of diabetes.
What kind of research was this?
This was a meta-analysis of studies investigating the influence of genetic variants on insulin and fat characteristics.
The research aimed to look at the variation in genes associated with patterns in fat deposits and insulin resistance.
Meta-analyses provide a useful way of summarising multiple studies looking at the same outcomes, in this case insulin resistance and storage of fat.
However, this type of study is only as good as the individual studies included, and any weaknesses of these studies will be brought into the analysis.
The studies included were population-based cohort studies, mostly from the UK and Europe.
Cohort studies are a practical way of looking at a link between two factors, but cannot prove one (genetic make-up) causes another (insulin resistance and location of fat deposits).
What did the research involve?
Researchers took 188,577 individuals from five population studies that analysed the genetic make-up of these individuals to identify variations in genes associated with insulin resistance.
They then looked at how the genetic variations played a role in cardiometabolic diseases.
This is a general term used to refer to diseases related to underlying problems with metabolism and bloodflow, such as type 2 diabetes and heart disease.
Researchers looked at the cardiometabolic traits and outcomes in people.
The levels of fat in certain areas of the body in those who were found to be at the highest genetic risk for cardiometabolic disease, including type 2 diabetes, were compared with those at lowest risk.
Leg fat mass was used as an indicator for peripheral fat, which is not in central areas.
What were the basic results?
Genetic predisposition to insulin resistance, through the 53 genetic areas, produced a higher risk of diabetes but lower levels of fat beneath the skin.
Looking at people with and without type 2 diabetes, the 53 genetic variants were associated with a 12% increased risk of type 2 diabetes (95% confidence interval [CI] 1.11 to 1.14).
No differences were found between genders or across body mass index categories.
People with a higher number of the 53 genetic variants were more likely to have a lower proportion of fat in their legs and a greater waist circumference.
How did the researchers interpret the results?
The researchers concluded that their findings “implicate a primary effect on impaired adipose [fat] function and a secondary effect on insulin resistance”.
They further added that their findings “support the notion that the limited capacity of peripheral adipose tissue to store surplus energy is implicated in human insulin resistance and related cardiometabolic disease in the general population”.
Insulin is a hormone in the body that helps control blood sugar levels. When resistance to insulin occurs, blood sugar levels and lipids (fats) rise, increasing the risk of diabetes and heart disease.
This study shows that 53 separate genetic variants were associated with insulin resistance, underpinned by an association with lower levels of fat in peripheral regions, particularly in the lower half of the body, but – conversely – possibly higher levels of fat around the liver and pancreas.
While the study has strengths, such as using a very large number of people, and did demonstrate a link between genetic variants and insulin resistance, there were limitations.
The data was compiled from a number of different studies, which may have each had their own limitations.
The majority were prospective cohort studies, which, while helping to show an association, cannot prove that these genetic variations cause insulin resistance.
There may be a wide range of other factors affecting risk of insulin resistance and subsequent type 2 diabetes, such as lifestyle factors, including eating unhealthily and not being active.
Other factors that can influence insulin resistance include age, being Asian or African-Caribbean, or having polycystic ovary syndrome.
Symptoms of diabetes include feeling thirsty, passing more urine than usual, feeling very tired and weight loss.
It is very important for diabetes to be diagnosed as soon as possible – see your GP if you think you may have symptoms.