Mechanism of action
Metformin can cause weight loss primarily due to its effects on appetite regulation via the hypothalamus, thereby reducing the number of calories that you ingest. It can also cause several GI side effects, which may indirectly affect weight loss9. Additionally, metformin can also reduce body fat secondary to optimizing insulin, glucose and glycogen, thus decreasing blood sugar levels and increasing demand of fatty acids used for energy.
Metformin primarily causes GI side effects like gas, nausea, vomiting, diarrhea, indigestion, and stomach pain. Additionally, long-term use of metformin is associated with vitamin B12 deficiency2.