Metformin has been the first line of diabetes treatment for over 25 years. It works by attaching to simple carbohydrates in our intestines, not allowing them to enter our bloodstream. Thus, our insulin level does not spike. When our insulin level spikes, it increases our chance of cancer and all other causes of death. But for our purposes, no spike in insulin means our bodies are not signaled to produce and store fat. In addition, when insult levels are lower, our body uses fat, not carbohydrates, for energy.
Metformin is a great way to eat a reasonable diet yet have your body express the simple sugars. Those who are on strict paleo diet and do not eat carbohydrates, Metformin will not be effective for weight loss. If you get loose stools, it tells you that for your body type and needs, you are injecting too many carbohydrates.