Too thin? Blame your parents. Now there's evidence that inherited genes can make you skinny — just as there is evidence for inherited obesity. While most of the research into body fat so far has been into the genetic causes of obesity there's now strong evidence that it goes the other way too.
The research showed that children of two thin parents had almost three times the chance of being thin as their peers: 16.2%, compared with 7.8% when both parents were in the upper half of the healthy weight range, 5.3% with two overweight parents, and only 2.5% for children with two obese parents. That's a population wide average of just 5.7% in the UK, where the study took place.
Keep in mind that thin here means something very specific, and more than just being lanky. The researchers' definition of thin is a weight that would be the adult equivalent of a BMI of 18.5 or lower, which is often characterized as "underweight". This BMI table can show you what weight levels we're talking about here.
There is definitely an environmental component to be aware of here, too. A family with thin parents is more likely to have smaller servings and a healthy lifestyle than one with obese adults.
What this research does show is that there's a genetic component to body weight, and it's not all about eating leafy greens and going on marathons. So go ahead, blame your parents for your size.