For one, an hour you spend exercising or walking around is probably an hour that you're not eating. Many Americans are constantly eating when they're at home, either mindlessly snacking or eating a huge meal. Given that you only have 8 hours between work and sleep, occupying yourself for 1 of those hours could mean a significant decrease in time spent eating.

Incidentally, this is why intermittent fasting works well for some people.

Diet is clearly a much more important aspect for weight loss. Exercise has many other benefits though.

When I lost 70lbs, I did so by deciding it was easier just to not consume the calories in the first place rather than trying to burn them off.

On my bike I have a power meter which uses strain guages and an accelerometer to calculate force x distance / time at the crankset so I have accurate calorie burn numbers.

Riding for an hour at the output a generally sedentary person can manage, I’ll burn sub 500 calories. Riding at my maximum output for an hour burns about 1000. Given that the recommended energy intake for a day is 2500, you can see what a difference that makes proportionally to what you can consume.

The fact that companies sell you these “features” in products is a scandal in my opinion, because it’s nothing more than a totally inappropriate guess. They always overestimate based on my experience when compared against actual output measurements, and that can only be harmful to people that are trying to use them to lose weight.

(Not to totally give up exercise tho' - there are other health benefits besides losing weight)

The only caveat I've learned is that weightlifting can make a dent. It's one of the few things where as you improve, you can burn more calories in the same amount of time instead of fewer (partly because you're doing more work as you add weights, partly because the muscle you build is more metabolically expensive to maintain).

I also had success restructuring my life so accessing food was way more of a hassle. Kept a mostly empty fridge. Meal prepped so only whole meals were there. Don't take money unless I know I need to buy something, found a few reasonable options at local sandwich places that became routine, etc.

I'd love to see a correlational study on fridge size and obesity. In America we buy SUV fulls of food, in Europe it's much smaller frequent trips, i.e. generally higher hassle per calorie.

Or more! When I started losing weight, my target was 1600 kcals a day. I learned that I was eating 1600+ calories __every single meal__, plus snacks. Pasta is the devil y'all.

And yet Italians are generally slim and healthy :)

In take is the kcal of the food times the digestion factor. The kcal out is the metabolic need, which depend on factors such as fat building vs energy usage, which in turn is influenced by stress but also things like dieting.

This is why counting calories can be an ineffective strategy for some while for others it is a good match.

Let say 1000 kcal in, and for an average healthy person 1000 kcal in metabolic rate.

For digestion, this person eat mostly proteins resulting in about 20% of kcal going into energy for the digestion system itself (proteins is relative hard to break down). Let also say that in addition, sloppy digestion and incorrect gut bacteria is resulting in additional 20% of the food never getting digested and resulting in feces. Result is a loss of 400.

If thats the whole story you have a person that is loosing weight despite keeping a diet that seemingly fulfills their calories need.

Lets now change metabolic aspects. Rather than suffering from bad digestion they are suffering from chronic stress with high cortisol, adrenal and other stress hormones. The body crave more food that cost less to digest, ie fat and sugar, insulin is spiking in order to get the body to take up more energy, the body goes into lethargic state in order to save energy, muscle and organ cell production is decreased in favor of fat cells. Instead of 1000 kcal in metabolic rate we might have 600 kcal, with now a surplus of +400 going into fat production.

The upper bound on bioavailable kcals is still 1000 kcal, but the numbers won't tell you if the person is going to loose weight or gain it, unless the person is in good healthy to begin with.

Intuition would make me wager testosterone levels of you average powerlifter would be in the higher ranges (necessary to build muscle), despite not generally being lean.