By Cynthia Sass, R.D.
January 20, 2011

If you're working out, watching what you eat, and still not shedding pounds, upping your intake of certain vitamins and nutrients may improve your results, according to recent studies. What's the catch? It's tough to get the amount required for weight loss from food alone. Here are three vitamin supplements that could help boost your slim-down efforts and feel great in your skinny jeans. Just remember to talk to your doctor or dietician before taking these, as some supplements may interact with some common prescription drugs.

Vitamin Supplement for Weight Loss #1: Vitamin D

If you're not getting enough of the sunshine vitamin, your waistline may be paying the price. Researchers from the University of Minnesota found that the higher the level of D that overweight men and women had in their blood before starting a low-cal eating plan, the more weight and belly fat they lost. How much do you need for slim-down benefits? Start with 400 IU daily, but consider getting a blood test to see whether you need more.

Vitamin Supplement for Weight Loss #2: Vitamin C

Want to use fat for energy instead of storing it on your hips? Vitamin C could be the answer. Arizona State University researchers found that exercisers burned more fat when they were given 500 mg of C in pill form every day for a month than those who didn't up their intake. How much do you need for slim-down help? If you're eating plenty of fruits and veggies every day, you can take a smaller amount of C.

Vitamin Supplement for Weight Loss #3: Calcium

Don't assume that your diet woes are due to a lack of willpower-it may be that you need more calcium. A British Journal of Nutrition study found that overweight women who took 1,200 mg of calcium a day lost 13 pounds more in 15 weeks than those who got a placebo. The researchers speculate that calcium makes you feel full, so you don't overeat. Best slim-down amount? Try 1,000 mg of calcium citrate a day, split into two doses, as your body can't absorb more than 500 mg at a time.