Why do some people stay thin even when they eat anything?

Have you ever wondered how some people manage to stay thin despite what they eat, when you seem to gain weight just by looking at a pastry? It turns out that the secret to their thinness is not necessarily a drastic diet, but rather a genetic quirk! A study, conducted by a team of Cambridge researchers, has revealed that some people have a unique genetic code that allows them to maintain their weight throughout their lives.


There’s a study that explains the phenomenon.

The study, published in the journal PLOS Genetics, is the largest of its kind to date. The team compared the DNA of about 14,000 people and separated them into different weight groups to discover how genes can influence a person’s weight. Sadaf Farooqi, Professor at the Wellcome-MRC Institute of Metabolic Science at the University of Cambridge, led the study which was supported by the European Research Council and Wellcome.


The objective of the “Study Into Lean and Thin Subjects”, or “STILTS”, was to examine how and why some people stay thinner more easily than others. Previous studies had shown that defective genes were responsible for severe obesity, which often occurs at an early age. This particular study, however, suggests that a combination of “thin” genes, or rather the absence of “obesity-related genes”, can help a person stay thin.

Genetics involved.

Professor Farooqi and his team, in collaboration with Dr. Inês Barroso of Wellcome, collected and compared the DNA of about 14,000 participants, 1,622 of whom were thin and belonged to the STILTS group. In addition, 1,985 volunteers were severely obese, and the remaining 10,433 were of normal weight.

Human DNA consists of a sequence of molecules called “base pairs”. The letters A, C, G and T represent the base pairs, and the chains of these represent the genetic regions. Our genes dictate how our bodies function, and variations, such as a C instead of an A, can have a subtle or dramatic influence on characteristics such as eye colour, hair colour and, of course, weight.

Comparative genetic variants.

The team came across several genetic variants that the researchers had already identified and associated with obesity. However, the recent study found new genetic regions that could be responsible for natural thinness.

By studying and comparing the DNA of the participants, Prof. Farooqi and his team came across several genetic variants that had previously been identified as causes of obesity. However, this recent study revealed new genetic regions, some of which are believed to be responsible for severe obesity, while others are believed to play a role in natural thinness. To find out how genes affect a person’s weight, the researchers took into account all the different genetic variants and established a genetic risk score.

Slimness is no longer a secret.

As they suspected, obese people have a higher genetic risk score that makes them more likely to be overweight than people of normal weight.

On the other hand, thin people have a significantly lower genetic risk score. They also lack the genetic variants known to be responsible for obesity. The study therefore showed that people who have always been slim despite their diet and lifestyle choices have to thank their unique genes.

A healthy diet is still essential, however.

Although genes can determine a person’s weight, this does not mean that one should not eat a healthy diet and live a healthy lifestyle.

Don’t be fooled by the results of the study! You can’t give up a healthy lifestyle just because you think your genes will work for or against you anyway. The study simply showed how genes may be responsible for different weight gain in different people. The odds can be stacked in your favour or against you. However, personal actions play a key role in weight management.