I'm assuming you were feeling pretty poorly to have been advised to get such a large amount of testing. You don't say what your age is -- did you get a colonoscopy because you're over 50 and it was recommended, or because something is going on and your docs are trying to figure out what it is? As to your food recommendations for yourself, it's not specific, but pretty much follows general guidelines. An exception is your focus on both calories and fat. There are fats to avoid but also fats to welcome. You mention omega 3 fats, but this is fat, so that's what I mean by your generalization of avoiding fat. All good sources of this beneficial fat are high in both calories and fat, such as fatty fish and seeds such as hemp, chia, and flax. To have this fat obviously the food source has to be high in fat, or if you take a supplement, it will be all fat. As for calories, what's more important for weight is how well you metabolize and digest a food, not the amount of calories. Again, some very beneficial foods are high in calories and fat, such as nuts, seeds, and fish, but you don't want to avoid them. It's a balance. As for your cancer fears, avoiding things that are bad for you can help, but it looks like you don't have cancer at this point depending on how the thyroid work up comes out. But the main anti-cancer foods are antioxidant rich foods, which are largely colored fruits such as berries and colored veggies, such as kale, collards, dandelion greens, watercress, etc. But there are a lot of antioxidants and almost all foods are high in at least one of them, so if you have access to variety that's good. But when you move from the general to the specific, it gets harder -- individuals differ. The part of your body that is the problem will raise different suggestions -- certain foods and supplements are protective of certain parts of the body more than others, while others are generally protective, such as Vitamin C rich foods. If you turn out not to have any cancer at least that can be found, you're in a different situation than if you do -- eating well is the best you can do to prevent, bu when you have, specific nutrients might be more useful and others might best be avoided. Everything depends on who you are at the moment when it comes to eating, because that's where the generalizations give way to the specifics.