While I do agree with you that sustained, high level activity requires and burns more calories, I think that the advice coming out of there, exercise is less efficient than diet for weight loss, is going to absolutely be true for the majority of gym goers who quite frankly are phoning it in whenever they work out.
Like, for example, an olympic swimmer may eat 5000-10,000 calories in a day, but they are spending around 4-6 hours a day in a cold pool training at a world class level (body needs to keep warm somehow regardless of effort.) But a normal person may only swim for 20 minutes at a much gentler pace. This person should still be eating in line with calorie guidelines and macros for age/sex.
The reality is that diet needs to be flexible based on results. Not losing weight? Eat fewer carbs or calories. Feeling tired and worn out? Eat more or exercise less based on your physique and goals.
I don't know how things are for anyone else, but it worked for me, shrug.
Attempts to loose weight by diet only all failed. To make it worst, there is also aspect of most common diet advice being plain wrong. It focuses on calories too much. It completely ignores what your body needs, so you end up in nutritional deficiency - this kind or that kind. And that will affect a lot and eventually you will stop diet and start to feel so much better and healthier after stopping it.
The calorie stuff is from both oxygen and deuterated water studies. You burn the same amount of calories and your system just shunts them around. The science on this is one of the few things in nutrition that is quite solid.
This has the effect, for example, that if you exercise a lot, this actually suppresses your immune system making you more likely to get sick.
Are you sure? 2000 kcal in 3 hours is 770 watts of power output.
Edit: Wikipedia [0] says "During a bicycle race, an elite cyclist can produce close to 400 watts of mechanical power over an hour and in short bursts over double that - 1000 to 1100 watts; modern racing bicycles have greater than 95% mechanical efficiency. An adult of good fitness is more likely to average between 50 and 150 watts for an hour of vigorous exercise."
I'm not, because the parent poster explicitly said "That's not based on made-up calories but actual work from a power meter on the bike."
Which seems absurd, hence my comment.
"You can't exercise your way out of a bad diet" - literally not true for a fuckton of endurance-sport athletes for whom the challenge is eating enough calories.
It's 100% true for people who think exercising for 30 min means license to eat whatever.
> So a good diet: takes less time than exercise, reduces calories more, and can save money
Yes, but endurance exercise over an hour or two brings its own advantages health-wise.
The real takeaway is that there are no absolutes.