I think what we're all missing is an education in the correct use of food. Our ideas today are shaped by the food industry, not by what our bodies need. Some people have just been educated correctly by their parents and others haven't. All those "it's in my genes" people and those "I can eat whatever I like" people are just liars. It simply works or doesn't work but they don't understand the basic maths here. While there are some mitigating reasons, most of them have little effect on the core calorific need of your body and the calorific inputs and outputs that you control.

What we really need is better food and diet education.

'Eat less, move more' is a great summary but this isn't a diet, it's a lifestyle change. If not, you'll just become a yo-yo dieter.

Every pound of fat on your body is around 3,500 calories. A healthy man with a moderate amount of exercise consumes 2,500 calories per day; or 17,500 per week. A fat person consumes more because your body works harder. A more sedentary person consumes less. Therefore, if your body needs 2,000 calories and you over feed it by 150 calories a day, you'll be 16 pounds heavier by the end of the year. Kill the 150 extra calories and you won't put on any more weight -- but you won't lose it either. So a diet is Phase I - it's an over-correction until you reach your healthy weight and then you move to Phase II - keeping it the same.

As you age, your calorific needs go down. As you become lazier, your needs go down.

So if your basic need is 3,000 calories per day and you only eat 1,200 calories, you'll lose 1,800 calories per day, i.e. 3 to 4 pounds per week. As you get thinner your rate of loss slows down though because your requirement declines. If you try and exercise to lose 1,800 calories per day you'll need to strap yourself to a treadmill for two hours. So I think dieting is about 80/20 in favour of food/exercise. There are benefits from exercise but there are pitfalls too - i.e. you eat what you've burned off and you over-exaggerate the calories or rely on what the machine says.

It's complex and I've been self-experimenting for 25 years but I say this after losing 60 pounds and with a BMI of around 26.5. Been there, done that and have the M, L, XL and XXL T-Shirts to prove it!