There is evidence that patients who take metformin while being treated with insulin for type 2 diabetes are not subject to the the traditional weight gain seen with insulin treatment. One hypothesis is that metformin has an effect on patients' energy intake. The short slide show above offers highlights of recent study that came to a very different conclusion.
Out M, Miedema I, Jager-Wittenaar H, et al. Metformin-associated prevention of weight gain in insulin-treated type 2 diabetic patients cannot be explained by decreased energy intake: A post hoc analysis of a randomized placebo-controlled 4.3-year trial. Diabetes Obes Metab. 2018;20:219–223.