1. Fats are bad for us.

Ah the quintessential food myth. While it's true that fat has the highest kcalorie density of all the macronutrients (9kcals per gram) fats have been given a false reputation. Most people believe that fats are the leading cause of stroke, heart disease, and diabetes. This stems from research done in the 1950s by a man named Ancel Keys. His research came to the conclusion that fats were the enemy, however his conclusion has been disproved time and time again.

We start with unsaturated fats. Monounsaturated fats are fatty acids with a single cis double bond. They are like the half way point between saturated fats and polyunsaturated fats. While not particularly good they aren't really particularly bad either. Monounsaturated fats don't contribute much to our lipid profile although they do slightly raise HDL and lower LDL. Monounsaturated fats also raise insulin resistance, but not as much as saturated fats. Polyunsaturated fats on the other hand are the bee's knees. These fats contribute to HDL cholesterol (the good kind) and have been shown to do a multitude of great things (Omega 3s are polyunsaturated fats). These fats contain multiple cis double bonds which prevent Van der Waal forces from holding multiple molecules together which in turn prevents it from crystallizing in our blood stream. Anyway all you need to know is the more cis double bonds the harder it is for the fats to crystallize.

Saturated fats in general have been targeted as the evil fat (along with trans fat, but I'll get to that) to avoid. In reality saturated fats are essential for keeping our body healthy. Saturated fats contribute to LDL cholesterol which in excessive levels crystallize and stick to arterial walls, however they are necessary for lipid transportation and cellular function. In fact our favorite hormone (testosterone) is a cholesterol derivative (meaning it is created from cholesterol).

So what about trans fats? TRANS FATS ARE THE DEVIL! Okay maybe not that bad, but they're still extremely bad for us. Remember how I said LDL cholesterol crystallizes and sticks to our arterial walls? Well trans fats are artifical fats created for the purpose of food preservation among other things. Now while that sounds great in theory when you look at the properties of trans fats the greatness of trans fats start to fade. What makes trans fats so bad is the trans double bond. Remember how I said cis double bonds prevented Van der Waal forces? Well trans bonds make them stronger. This in turn raises the melting point of the substance allowing it to crystallize at lower temperatures.

So what should I do? Trans fats should be avoided at all times. While a little won't kill you the more you get away from them the better off you will be. While saturated fats shouldn't be consumed in excess avoiding them is a generally unhealthy practice. Monounsaturated fats can be more considered the neutral fat and is more of a kcalorie adder than anything. During a steroid cycle lipid profile becomes more LDL focused unfortunately so while on cycle lower saturated fat consumption (DO NOT ELIMINATE IT) and raise polyunsaturated fat consumption.

Overall all good things in moderation.

References: All of this was pretty much common knowledge to me since organic chem 1, but I'm sure you'll find wikipedia to agree.

http://en.wikipedia.org/wiki/Trans_fat
http://en.wikipedia.org/wiki/Unsaturated_fat
http://en.wikipedia.org/wiki/Fatty_acid
http://en.wikipedia.org/wiki/Omega-3_fatty_acid
http://en.wikipedia.org/wiki/Omega-9_fatty_acid