Yeah, there are many polarized views about the issue. Have you ever wondered why?
I'm not to bash you or anything, but to throw in my opinion about the issue. Ironman is a wise fellow, said alot of things I would have said and agreed to, but let me give my 2 cents.
A calorie isn't a calorie. That's a given. Not everything you eat will have the same results on digestion. Not even close. There are several things in physiological level why all the grams of nutrients aren't the same. Calories in - calories out is not a way I would go. Atleast by a longer shot.
Caloric restriction works only so far. A small one is alright (200kcal) reduction from what you truly need. If you cut back on everything, no matter the nutrients, for a thousand calories, you'll be in trouble. The body still uses over 2000 calories daily, there's nothing you can do about it. Unless you severely restrict your calories and exercise much. Then your body will seriously trigger into starvation and slower your metabolism down a notch. Then you use less energy. When there is a noticeable caloric defiency day in and day out, the body notices it and tries to reach balance. That's a fact. When you end your "diet" and try to eat normally, you will gain fat because of the sad fact your metabolism is still very degraded from the starving. The biggest loser constests are the best example of this fact.
Exercise changes everything. When you exercise, you use a way lot more calories. Nutrients come less important; the muscle absorbs anything it can, no matter what you eat. Severe calorie cutting and exercise will most likely lead to recovery issues and loss in muscle mass as well as fat.
I think carbs are the primary fuel for exercise. When we think about optimal performance and recovery, carbs should belng to your nutrition pre-workout, during workout and after workout. The windows in before and after can vary from long to short depending on exercise and goals. Nowhere else do you need carbs except for that window. That's a sad fact, and the main reason why the world is so obese. Carbs are evil for non-exercisers. Why? Because they are so easy to overconsume. Eat a bag of candy (100-250g or even more), that's what many people do several times a week. Well, that one bag can give you over 60-150g of carbs instantly. Can you imagine what that does in your body? Try to consume that much fat or protein in a short period of time. It's impossible. To eat that much protein, you should binge down over 300-700g of meat in a relatively short time. And still it wouldn't have the same effect on your body, because the nutrients aren't the same. The same goes with fat. You just can't overeat too much fat that easily.
Then again, I would like to point out that in moderation everything is alright. You can eat low-fat and high carb and still not gain pounds. Atleast some people can. Especially for athletes this has been a staple for decades, and it seems to work as well. The body needs energy and nutrients. If you give the body the right amount of those nutrients, it'll stay the same. If you exercise, you need more nutrients. If you sleep all day, you shouldn't be eating that much. Even though the point of using the energies and calories you have eaten is relatively true, it needs moderation and thought for optimal results. It's not about the calories, and neither is caloric reduction. They both happen because of the amount of nutrients you should consume. Let's think it that way. For general weight loss, there is a rule of thumb to lessen the amount of calories eaten. How does that happen? By cutting the sugars and excess carbs. Tadah. Caloric reduction shouldn't lead to nutrient cutting, nutrient cutting should lead to caloric reduction. The point in burning more than you eat lies behind the fact you must first burn of the glucose and carbs from your body before the fat gets it's turn (in general). So, wouldn't it be easier to burn more than you eat if you already cut back on carbs on average non-exercise days. Then the body can concentrate on burning off the fat. Plus, I don't think we even have to mention what Insulin bursts do to fat loss. There's another reason why caloric reduction with high amount of carbs doesn't work so well.
So instead of daily caloric defiencys, I'm still in favor of carb cycling. It involves lower calorie days and higher calorie days, but it's not about the calories. It never has been.
Physical Preparedness Coach
Co-Owner of UniFit Oy.