If I go to GNC, they have vitamins that are supposed to increase metabolism. Are they effective?

Thanks a lot. I was just wondering because if I go to like GNC and they have vitamins and stuff that are supposed to increase metabolism. So I was just curious is as to whether or not they are at all effective.
Forget supplements unless you eat less than 1200 calories a day, then take 1 multivitamin. Chromium picolinate is being touted as increasing metabolism and to date, there is no supporting evidence other than chromium is necessary to make insulin, which is used to move glucose from the blood into cells. And don’t listen to people who have no formal education in nutrition. Some states regulate who can provide nutritional advice because of all the misinformation being given out over the checkout counters. Why don’t you read Nutrition Today magazine, which should be available in your local library?