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Est. $20 per week
January 2012
by ConsumerSearch

  • Short-term weight loss
  • Shakes, snacks are nutritionally sound
  • High dropout rate
  • High cost
  • Lack of variety in available foods

Not all dieters have time to count every calorie or prepare nutritious meals. Slim-Fast's 3-2-1 plan is nutritionally sound and has been evaluated in a number of clinical studies, where experts say it can lead to similar weight loss as other popular commercial diets. In one study, subjects lost an average of 13 pounds in six months. But even though most people can stick with Slim-Fast for a couple of months, studies show most can't adhere to the program for longer periods, and dropout rates are high.

To follow the full diet, you eat a 500-calorie balanced meal for dinner while other meals come from two Slim-Fast meal-replacement shakes or meal bars each day, and three 100-calorie Slim-Fast snacks a day. The plan is convenient, participants say, but the cost can add up quickly and the shakes and bars can become tiresome. If you prefer a more structured approach, Weight Watchers (Est. $20 to $30 per month, plus weekly meeting fees) is the top-rated diet overall.

The Slim-Fast weight-loss program is included in's latest comparative review; it also appears in a comparison of commercial diets published in the British Medical Journal. We saw user comments posted on and

Our Sources


Editors discuss and rate seven weight-loss programs, including Slim-Fast. Diets are assessed on their nutritional soundness and the results of clinical studies.

Review: Top Diets Reviewed, Editors of, May 2011

2. Public Health Nutrition

This study follows 300 overweight individuals as they use Slim-Fast, Weight Watchers, the Atkins Diet or Rosemary Conley's "Eat Yourself Slim." Each dieter achieves a similar weight loss, regardless of the diet.

Review: Comparison of the Effects of Four Commercially Available Weight-Loss Programmes on Lipid-Based Cardiovascular Risk Factors, L.M. Morgan, et al., June 2009

3. British Medical Journal

The BBC's "Diet Trials" is a reality TV show and accompanying medical study that evaluates the weight loss of nearly 300 dieters on five different diet plans, including Weight Watchers and Slim-Fast. Results suggest that Weight Watchers is easier to stick with over the long haul.

Review: Randomized Controlled Trial of Four Commercial Weight Loss Programmes in the UK: Initial Findings from the BBC "Diet Trials", June 1, 2006


WebMD interviews a number of nutritional experts in this lengthy Slim-Fast review. Editors say meal-replacement diets like Slim-Fast can lead to short-term weight loss, but they caution that the diet can be hard to stick with, especially if you don't like the shakes.

Review: The Slim-Fast Weight Loss Plan, Editors of WebMD


Slim-Fast shakes receive only 3 stars out of 5 in more than 170 reviews. Some users complain about a metallic aftertaste, but others say Slim-Fast products cut their hunger and help them shed pounds.

Review: Slim Fast Shakes, Contributors to


More than 80 reviewers give Slim-Fast an overall rating of 3.54 stars out of 5. Some are pleased with how quickly they lose weight without having to count calories or follow complicated meal plans. Others say the shakes get old fast, and that Slim-Fast is best for short-term dieting only.

Review: Slim-Fast Reviews, Contributors to

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