I already have. It's the same every time, there is no magical disease that makes your body defy the laws of physics.
Sure, there are health conditions especially those involving hormones that increase your appetite so you consume more calories, but there is no such disease that defies thermo dynamics and makes you burn a meaningful number of calories more than any other person. There are differences from person to person but the numbers we are talking are negligible.
The key to sustained weighloss is education, very few people have any idea of the true number of calories they're consuming because frankly their diet is total garbage. Typically high in UPF and calorie dense foods where the odd extra untracked gram here or there cumulatively makes a huge difference.
It's not until it's pointed out to an individual that the penny drops, not that it is necessarily true in this case but the extra calories are coming from somewhere. There is not an adult person on the planet who can consume 1000 calories a day consistently and not lose weight, the math doesn't math.
Typically someone will eat 1000 cals per day for 3-4 days, fall off the wagon because it's so unsustainable, binge and not track what they're eating and low and behold their average calorie intake is actually higher than if they'd have just consistently eaten a healthy number of calories each day.
I'm a qualified nutritionist if it makes any difference to you. This forum is full of people who will perpetuate myths and promote weight loss jabs/fad diets etc, encouraging people to develop deeply unhealthy relationships with food, and then you get the other crew such as yourself who refute every single piece of evidence thrown at them.
My best advice would be to take your weight, heigh and measurements to calculate your TDEE, factor in your daily activity levels and adjust your calories to suit and sustain a calorie deficit of 500 calories per day.
OP if you feel comfortable doing so please share your height and weight so we can make meaningful recommendations.
The 45 min brisk walk a day you're doing will be burning somewhere in the region of 200-300 calories for an average woman. There's no way by virtue of being alive your body is using less than 700-800 calories to stay alive...