Ok, well, I understand all that. I have a background in living systems. If you metabolism slows, you don’t burn as many calories. Red’s statement stands—his observation is correct in that if you consume a thousand and burn 1100 you will lose weight. He made no reference to metabolic changes. Also consider that when you ramp up the exercise routine you also ramp up metabolism and burn calories at a higher rate. Personally, I have pretty much maintained my same weight for about 40 years by adjusting how much food I consume, and how much physical activity I engage. It does take a good bit of effort. Starvation diets are mostly useless in the long-term.
Sure; from a purely mechanical standpoint, if you burn more calories than you consume, you have to lose weight (note that whether the loss is muscle or fat is not specified). However, it isn’t that simple in practice. For example, if your body goes into a conservation mode, you simply don’t have the energy to exercise at a high level.
Also consider that when you ramp up the exercise routine you also ramp up metabolism and burn calories at a higher rate.
Yes, but to ill effect if you ramp up your exercise routine while cutting down on caloric intake. Then you just overtax the body and make it ill. One of the few actually SMART docs I know pointed that out to me, that I was messing up when I'd swim an extra mile or so without increasing my NUTRITION intake to help my body meet the demands such efforts make on it.
I took his advice and benefitted: if you're going to increase your exercise, be sure to also increase the GOOD NUTRITIOUS foods you eat, primarily proteins, fats, fruits, and non-starch veggies, and maybe even increase the carbs a bit as well. I couldn't figure out why I was getting so tired later in the day, even though I was well hydrated. Once I took that doc's advice and started consciously eating a little more than I might otherwise in the protein and veg. and carb depts., the problem disappeared.