Obesity is closing in on smoking and alcohol as the top killer among lifestyle diseases. Over 25 percent of the world is overweight and in countries like the UK and US, that number is approaching 70 percent. It is correlated to things like heart disease.

Is it a genetic issue, and therefore exculpatory? A new paper hopes to show that. The authors analyzed brain scans of 1,351 young adults across a range of  body-mass index (BMI) scores. They found that the overall volume of the hypothalamus was larger in overweight and obese people. They declared a significant relationship between volume of the hypothalamus and BMI.

The question is whether or not the correlation arrows are all wrong and the changes are not causal but just related to inflammation. Or even meaningful, since it is only MRI and statistical significance is an easy crutch when looking at pictures of brains.  To add to the confounders, most assumptions about the brain and appetite used animal subjects for conclusions, and animals are not little people. There is some biology in common, but humans have 50 percent DNA in common with a banana so we can't read a lot into mouse and worm studies. MRI interpretations are even less rigorous.

Your brain does not cause this, nor do chemicals in the pizza box or anything else except calories.

Most people do not eat when they are hungry or 70 percent of a country would not be fat, the stomach is a muscle and anyone who has fasted for more than 24 hours will tell you that muscle adjusts fast and they stopped having 'hunger pangs' a day later. Given that, drilling down on a section of the brain that might be linked to appetite is a fine exploratory effort, but not relevant scientifically yet. Your brain does not make you overeat. Your hormones do not make you fat, nor do the chemicals in the pizza box make you obese. Yet correlation studies have all claimed those things.

Many who lack impulse control want to medicalize their behavior - medicine for everything is why America leads the planet in prescription medication. The US CDC even invents conditions like prediabetes claiming it will will raise awareness about obesity when really all it does is give drug companies a giant subsidy.

We're gradually converging on a world where people will stop claiming minute differences in biology are meaningful. Sometimes even gigantic differences in biology are declared irrelevant. Then we can tackle the obesity problem by realizing it is an evolutionary and cultural relic. Until the 1980s, the world was believed to be Malthusian and mass starvation was a growing season away. Instead, science has made so much progress in yield and affordability that even the poor can get fat. Yet only two generations removed from media-created Population Bomb Hysteria, so people still treat food like it's a celebration. It is now a commodity. If we aren't obsessed with using a washing machine all of the time, there's no reason to feel that way about cheeseburgers.