At the very least, you do yourself some good by avoiding the food and drink that are clearly dangerous to your health. That starts with anything that contains lots of sugar. Don’t be confused by claims of “pure and natural.” On the header of this website is a photo of a sugar factory. What comes out of that factory is tasty and clean, but it’s not good for you in large quantities.
Any form of sugared drink will kick up your insulin and send your liver into fat-making overdrive. Soft drinks, sugared coffee beverages, fruit juices; all the same. In fact, Robert Lustig likes to point out that orange juice has even more fructose than a sugared soda. Eat the fruit. Don’t drink the juice squeezed out of the fruit. Without the fiber of the fruit, it’s toxic.
Keep an eye out for processed food and drinks with added sugar that your body absorbs quickly. That elevates your insulin, which tells your body to store fat. Elevated insulin makes you eat more, too. That’s why a fast food meal with a sugared drink is so effective at helping you put on weight. That combined with nasty effects of the fructose portion of the sugar directly on your liver and organ systems.
Breads and pastas are made with the modern flours have had almost all the fiber removed. They digest too quickly. Donuts and pastries are amazing combinations of dough, sugar, and fat. I never met a donut I didn’t like. After my second run up Mt. Lemmon from Sabino Canyon many years ago, I immediately ate five donuts. I ignore the convenience store bakery displays these days. I did the same trek over 30 years later in a ketone-adapted (see High Fat) state in 2013 and didn’t miss the donuts. Here’s what that trek looks like on a topo map, done without any Gu packets or other sugar sources the carbohydrate eaters use. Click and the map should get bigger in its own window.