1. Calorie Total
2. Calorie Composition
1. If you have a deficit of calories, eat less than you use a day, you will lose weight, regardless of WHAT you're eating. That is, how much you eat is more important to total weight loss than what you eat.
There's no way around it. If you want to lose weight you have to consume fewer calories than you use.
The thing is, it's probably NOT just about losing weight. The goal is probably to lose weight permanently and to be healthier. They're not necessarily the same thing!
2. If you eat "healthy" foods your digestive system will function better as will your immune systems and probably every system in your body. So the quality and composition of the food you're eating is very important but without #1, it won't help you lose weight.
The best is to do both...eat reasonable portions of quality food. Then, you'll get the double whammy! That is, will you lose weight and be healthier aside from the weight loss.
For me this all has to do with Portion Control...that's my most difficult hurdle. Cutting out certain foods is NOT too difficult for me. Snacking isn't too difficult for me either, provided I get the proper amount (1) and type (2) of food at my meals and planned snacks.
One thing I've noticed is that the less prepared the food I eat is, the more likely I am to get both aspects honored appropriately. That is, if I buy whole foods and use them for my meals instead of buying processed food items, I'm going to consume fewer calories while eating better food. The kicker is that, usually, I will be more satisfied. That means, portion control is easier.
The thing I've noticed with portion control is that there are two motors at work. The first is hunger. If the portion is appropriate and I'm still hungry sometimes I ate too fast. Waiting 20 minutes or drinking more water sometimes helps. Sometimes, I'll still be hungry after both of those and will permit myself something else to eat. I am trying to get away from eating seconds because of the second driving force in portion control.
The second driving force is more difficult because it requires only will-power. The second thing that causes me to disregard portion control is desire...I like the food and want more of it because it tastes good. I'm not longer hungry, in fact, I'm full, but I want more because it's good. Ephemeral experiences are like this. We can't store them up for later. It's here now and then it'll be gone, so get while the gettin' is good!
This takes a philosophical approach. We must balance current pleasure with the prospect of future pleasure. So, perhaps knowing ahead of time that a meal is going to be delicious will help us to savor it and appreciate it while helping us restrain from gluttony.
So, portion control is a tricky thing. Having a game plan is a must!