They make you nauseous, and sometimes throw up, and basically negates your desire to eat, so you eat less.
I always thought this was comparable to bulimia or anorexia.
When I feel the need to lose weight, keto and fasting works for me. Just keep the calorie count as low as you can and it's amazing how fast your body will consume its own fat to keep the books balanced.
48 hrs after I started Ozempic injections I remembered that I needed sustenance to maintain life at its current level. Then my stomach shrank to 1/4 its size. No one realizes “smaller portions” is a colloquialism for “if you eat more than a tablespoon, YOU WILL VOMIT harder than you can ever remember in your life”.