I have been asked to answer a question on Quora.com on weight loss, and this is my answer:
People's metabolism differs. It is easier for some to gain than others. Also, your metabolism decreases on average about 1% per year after age 27. So you must eat less, or exercise more.
Weight gain is mostly calories in vs. calories out. No matter what you eat, proper eating habits and exercise cannot be replaced.
Also, there is a tremendous emotional factor with weight. The easiest way for women to lose weight is to get divorced, in my experience. (I am not recommending this, just an observation). After divorce, the need to meet someone new can force women to lose weight...to look their best. And some people eat as a psychological crutch.
However, the best book I have read on food is Michael Pollan's "In Defense Of Food". In summary of this book, he says, "Eat food, not too much, mostly vegetables." - A 7 word summary of dieting. By food he means only food found in nature, not in the processed isle of the supermarket.
If you would like what I do to maintain a normal weight, I would recommend:
Eat 3 meals a day, preferably at the same time.
Eat when you are hungry, drink when you are thirsty.
Never snack - if someone offers you something, turn it down.
Drink water or other fluid with your meal, you will eat less. The water fills your stomach up faster, and your brain will get a message to stop eating.
Eat slowly, and enjoy your food. I like to read when I eat - i find it relaxing.
Eat dessert only after a meal.
No or limited alcohol - remember it is high in calories.
Don't skip meals.
Discipline is essential in maintaining your weight; remember, it is up to you.