Or using drugs...
Weight loss can be done with food only.
"Reducing calories" is NOT a good way to loose weight and KEEP IT off as it's unsustainable due to hunger.
The general dietary patterns that one finds across tribal people/historyical are two: 1) high carb, low fat 2) high fat, low carb.
Pick one and stick to it.
As long as you mix carbs and fats the body goes crazy since due to the Randle cycle the body cannot effectively process both at the same time + it causes blood sugar buildup.
Guess what kind of a diet is the Western diet? The one that MIXES fats and carbs in HIGH AMOUNTS (eg 40% carbs, 40% fat, 20% protein as calories).
Such a diet is cancer.
Also do note that some obese people will NOT see weight loss for the 1st few months at all if they have a chronicaly elevated insulin, which can take months to normalize. And until insulin falls down to a normal level it's IMPOSSIBLE to lose fat since insulin is KEEPING the fat in the fat cells.