How do we avoid obesity?

Stop eating fatty foods and exercise regularly.

self-control and common sense
Eat Healthy!

And Exercise!

And you should be good.
avoid sugar and chips,chocolat and excersice reggularly. Don't forget to eat healthy. But sadly if u have genetic obesity means if alot of people in ur family is fat u may not be able to avoid it. But me im skinny and all my brother is a lil fatties (not being mean) but that is because he eats like a pig so i think it's about how much u eat and what u do.
Eat heathy foods. Stay away from Mc Donalds and all those fast food places and get plenty of exercise! Now, if I can only practice what I preach!
Balance you food intake and your exercise output and you will be all right. It sounds difficult but rather than dieting learn to measure you food portions so you will know the amount of your input. There are some very good diabetic diets or weight watchers type book that will tell you the number of calories per serving of particular food portions. Once you get onto doing this you can control your weight but it takes discipline.
Eat less and move more, 80% of what we look like is how much we eat. You can eat the foods that are good for you, but if you eat to much you will get fat. The more muscle you build the more fat you will burn.