One caveat, though: humans are designed to be omnivores (animals that eat everything); you can become a healthy vegetarian, but don’t end up an unhealthy vegan. Most of the vegan foods sold are chemistry labs in the form of fake bacon. Beware!
No processed food
I do not trust the food industry. I do not like eating chemicals that I cannot pronounce but that are written on the package. So, no prepared foods (veggies and fruits excluded); nothing from a tin, nothing frozen, nothing in an air-tight package (dairy products are OK).
Eat vegetables and fruits
We should all eat more of these. Specifically, we should eat more raw vegetables and fruits, since our bodies use more energy to break down raw food products and that helps with maintaining our calorie intake.
Regarding fruits, we have to be careful. Some fruits are very high in calories (such as bananas and figs) but have high amounts of nutrients (such as potassium). Other fruits are low-calorie water containers, such as watermelons! Want a treat every day? Try dried fruits and nuts. A handful of each.
Meats, fish, shellfish and protein
Protein is a basic and valuable food source, and meats and dairy products are excellent sources of it. Our bodies expend a proportionately large amount of energy to digest proteins, so they provide for a sustained release of energy. Any breakfast should include a healthy dose of protein to sustain us during the day and prevent the wild blood sugar fluctuations that occur after eating a donut!
Eat carbohydrates in moderation
Bread, rice, pasta, sugar, fruit juices—we are hardwired to eat basic carbs. Our brains love sugar (glucose), and it acts as a quick fix for hunger. As a food source, though, carbohydrates are a poor choice, leading to a fast and short-lived rise in blood sugar with its accompanying high. The carbs not used up in our heart and brains are delivered to our liver for storage and transformation into fat, unless we use them up in exercise. Use carbs as a source for a quick energy boost before sports or an exam/brain workout! Don’t use carbohydrates as your main source of calories. You will become sleepy at first, and then fat!
Eat fats (unsaturated) in moderation
Like carbs, our taste buds love fat. Fat such as butter and cream tastes good! As a food source, it must be broken down into sugars for use (that’s how the Atkins diet works), but along the way it causes toxic byproducts. Our bodies use fat as long-term energy storage. If it is flowing freely in our arteries, they will clump up and clog them. Lower your intake of fried foods if you want to lose weight and stay healthy.