If you put more food in a bass pond the bass will grow fatter.  Like going to gym, people need to train on eating just as hard as exercise.

Studies show that even obese people can have higher life expectancy than thin people.

http://www.independent.co.uk/life-style/health-and-families/features/why-being-overweight-means-you-live-longer-the-way-scientists-twist-the-facts-10158229.html
Obese being defined as a BMI of 30 and above. That means those with a BMI of 31 are clumped together as part of a group which includes those with a BMI of 50 – and above. What does this tell us about the health problems of having a BMI of 31? Well, absolutely nothing.

BMI between 30 and 35 lived longer than those of so-called "normal" weight.