Healthy eating

Fruit and vegetables should be the largest portion of foods you eat. It should be a larger portion of your diet than dairy, which should be a larger portion of your diet than grains, which should be a larger portion of your diet than meat and pulses, which should be a larger portion of your diet than foods high in fat, sugar, and salt.
Some people think sugar is just a flavoring material, but it's not. It's bad for you. Scientists are looking for alternatives, and there are some like honey, stevia, neotame, sugar alcohol, sucralose, saccharin (banned in Canada), and cyclamate (banned in the US). Some (.such as Stevia) are not confirmed to be safe but seem to be good. And many of these alternatives have some negatives compared with sugar. But honey is obviously a healthy alternative to sugar, and is used in honey Graham's.
Also, don't eat genetically modified foods. They are said by some to be better, but the consequences of genetic modification include cancer.

Losing weight

You'd think that sugar is the way to lose weight, because it speeds up the body. The faster you move, the more fat you burn. But it does not work like caffeine. Excess sugar in the body converts into fat. Sugar decreases metabolism. It's the sugar, not the fat, that makes you obese. But since you heard that excess sugar converts into fat, you'd think that excess fat is burned by the body. But unfortunately for all of us, it's not. We don't know why. You may be thinking "shouldn't metabolism increase with mass of fat in the body? Shouldn't it be that, the higher the mass of body fat in the body, the higher the metabolism?" Unfortunately, that's not the case. We don't know why, but it's unfortunate for all of us.
Don't eat late at night. That's the way to gain weight. When you eat sugar and fat, and then sleep, the fat settles and is not used as energy. You might be bugged by that. Eat in the morni and afternoon. Because you move and burn the fat you ate. In fact, a high-fat, low-carb diet could lose you fat. Another good thing for losing weight is high protein diet.
We'll have to find technology to genetically engineer humans and change there DNA. It is physically possible, we just haven't found the way to do it. Make it so sugar increases metabolism. Genetically modify humans to make them stronger, more intelligent, and faster, and other things. Genetically modify humans for a stronger immune system. It is too bad if we can't do it.

Saturated vs. unsaturated fat

Butter contains mostly saturated fat, and margarine contains much unsaturated fat. Saturated fat is bad for you, because your body converts it into a type of cholesterol that can clog your blood vessels. Unsaturated fat doesn't do that, but it can still be bad for you in excess amounts.

Some more things

Eat whole wheat, not white bread. Whole wheat contains fiber that is good for your digestion.
A vegetarian diet actually can provide enough protein. But when excluding eggs and milk, you have to eat things like rice, pulses, and other things.
Too much of anything is bad, even good stuff like fruits and vegetables. You need to stop when your body says enough. Don't overindulge.
I might add some things later. Any questions, comments, or disputes? Say so in the comment.