Wow! There's a lot of mudslinging in here.
I don't care how good a shape you're in, how ripped you are, how much muscle you have doesn't make you THE expert in diet advice. Yes, you may have a little more of an inside track of what works for YOU. Yes, we all know that broccoli is healthier than chocolate chip cookies.
Calories are calories except when it comes to type of calories. I don't know how many times I've heard registered dietitians tell people that calories are calories and as long as you don't take in more calories than use expend then you'll lose weight. Sure I'll agree with that in a very short term but if I have a diet 60% carbs 20% protein and 20% fat and I'm taking in 2000 calories a day and I cut it back to 1500 calories a day but using the same ratios yes I'm going to lose weight and in turn I'm probably going to lose muscle mass along with it. If you're not taking in the right macronutrients your body can still lose weight but you're going to lose it proportionately fat and muscle and depending on how far you cut the calories and how much you work out and breaking down muscles will eventually flip the switch where you're going to start burning more muscle because you're not feeding them properly.
I didn't an experiment about 10 years ago. I took in 5000 calories per day for 6 weeks. 70% of my calories came from protein, 20% came from fats 10% came from carbs.
I took in 210,000 calories during that 6 weeks and based on 3500 calories per pound I should have gained 60 lb. Now of course, I had to take out my BMR out of the equation which at that time I had a dexa scan done to give me the amount of calories my body Burns each day based on my body composition. At that time my metabolic rate was 1460 calories per day or in the end I should have gained 42.48 lb but I ended up gaining a total of 2.3 lbs I was a hell of a lot thicker, body fat percentage went down four points
I would bet every cent in my pocket, which isn't very much, and say if I change those ratios to 80% carbs 10% fat 10% protein I would have gained a lot more weight and would have not had the fat loss that I did.