It's a fact that it's harder for women to lose weight than men in certain cases. Their point was that "caloric deficit" is different for each person, and sometimes dramatically so.
Every living person that is maintaining their weight can eat 500 kcals a day less than they do now and they'd lose weight.
a) Doesn't really eat 1000 kcals a day if she's active, and should, instead of building a diet by counting calories (doing which she's prone to miscalculation), simply eat less of whatever she usually eats. b) Doesn't need to lose half a kg of fat every week.
Most online calculators are veeery optimistic (off by >500kcal). If you take the general advice and only restrict to a 500kcal deficit, you won't see much happening :/
The body can adjust its usage of calories way down in the event of a perceived famine, making the amount of calories consumed no longer contain a deficit.
The RMR can change during a diet as both fat and muscle require maintenance, and you nearly always lose both during a period of deficit. This can make maintaining a significant deficit very difficult
Finally, there is evidence that people who have lost significant weight have a reduced metabolic weight (and hunger for more calories) even five years after they completed their dieting. This may explain why the failure rate of people >100 lbs overweight losing and maintaining is nearly 95%
The hormone mix basically tells your body to store some percentage of calories in as fat. When young and/or fit, this percentage is low. Calories above your burn rate are stored as glycogen in your muscles, giving you usable energy stores that will be used when you exercise.
When older or fat or both, calories above your burn rate go to fat cells waiting to fill back up. As the weight packs on, the percentage increases and more and more of the calories you consume are going to fat instead of being burned. Your caloric burn alotment goes down. You lose muscle density. Testosterone goes down, and the percentage of calories dedicated to fat stores climbs.
So it is still true, calories in < calories out to lose weight. But perhaps it would be better to say “calories in < (calories out + calories stored)”
Where calories stored will vary and for fat people it’s much higher than fit.
A fat man can eat the same food and calories as a fit person who does not exercise, and gain weight and feel tired while the fit person feels an energy boost.
There's also the fact that muscles burn fat whereas fat begets fat storage.
I believe metabolism does slow year over year once you get to a certain age, but it's difficult to find data on that.
Exercise is important, and people should exercise because they get benefits even if they don't lose weight, but you should stop saying it's useful to reduce weight.
We think that people heavily over-estimate the amount of calories burnt by exercise; they under-estimate the amount of calories they eat; and exercising gives people "permission" to eat more calories than they normally would.
http://www.cochrane.org/CD003817/ENDOC_exercise-for-overweig...
You are correct that people frequently overestimate how many calories they burn working out, and that they then eat more as a result - both because they think they've earned it, but also because exercise stimulates your appetite. But when you understand these instincts and stick to the diet, exercise will help you lose weight more quickly.
And, of course I can question curiosity. We're in the internet age. If you have a basic question, ask google.
When somebody presents an opinion that seems to go against the general scientific consensus, no, I won't just google it, I'd rather ask what they base it on.
/s
Of course each of us is unique, and also changes over time, so efficiency of both inputs and outputs varies.
I believe you meant that its mentally hard to restrict one so much in later age to suffer from hunger enough to lose weight, but technically its doable and happening in millions of instances around the world all the time (ie due to long term illnesses).
Exercise helps tremendously of course, and everybody should do enough of any healthy type every day to get sweaty (and more). But it isn't necessary to lose weight, not at all, at any age.