Regarding messing with your gas exchange: The body is well adapted to 21% O₂. If you flush the CO₂ of of your lungs (which you can do without the tank, just hyperventilate) you'll actually bugger up your blood's pH (CO₂ in water is carbonic acid), and you'll get pins and needles and nasty cramps in your hands.
So probably avoid that.
As far as weight loss goes, the only method that works is to modify your diet and decrease your dietary intake. Doing this is, often, hard. Food has many functions in our body, we don't often eat out of genuine hunger. A psychologist can be very helpful.
There seems to be reasonably good evidence that once BMI exceeds some number between 35 and 40 it's almost impossible to reverse that by willpower alone. In those cases the combination of willpower and bariatric surgery (but not surgery alone) can be effective.
Source: I'm a doctor in Australia. I lost 50kg through bariatric surgery, with ongoing psychology to support the behaviors required to maintain a healthy weight.
I've tried eating less for weight loss, but when I do I sometimes (multiple times a week) feel really low on blood sugar (break out in a huge sweat and feeling the shakes) and the only thing that helps is eating.
(I've tested for diabetes and it's not that...)
So on these threads that say "just eat less", is there a way of eating less while preventing that crappy, hypoglycemic feeling?
(I exercise a lot, so I've got that covered... I just have a constant need to eat, although I eat healthy these days and have mostly stopped snacking).
The reason I suggest keto is due to the energy being less spiky and available over longer periods of time. I eat twice per day, a bowl of skyr (a cheese, yogurt consistency) with pecans, walnuts and a little vanilla along with a healthy helping of lactose-free heavy cream for lunch and feel absolutely full till dinner. For dinner I eat a meal where I cook from raw ingredients using lots of cream, butter, fat meats or fish. I don't especially measure the evening meal but I try to keep myself under 2500 kcal total for the day. I'm only hungry a little bit in the morning. I tackle that with drinking lots of water as soon as I'm at the office.
Not saying that's going to work for everyone. Works for me.
So probably avoid that.
As far as weight loss goes, the only method that works is to modify your diet and decrease your dietary intake. Doing this is, often, hard. Food has many functions in our body, we don't often eat out of genuine hunger. A psychologist can be very helpful.
There seems to be reasonably good evidence that once BMI exceeds some number between 35 and 40 it's almost impossible to reverse that by willpower alone. In those cases the combination of willpower and bariatric surgery (but not surgery alone) can be effective.
Source: I'm a doctor in Australia. I lost 50kg through bariatric surgery, with ongoing psychology to support the behaviors required to maintain a healthy weight.