The Slim Fast approach to weight loss involves replacing two meals with Slim Fast shakes, eating two Slim Fast snack bars, and eating one regular meal of about 500 calories every day. The plan can be effective in the short term, because your overall calorie consumption will be lower than usual, but followers are likely to regain weight once the diet is over. As to whether the Slim Fast foods actually suppress your appetite, it depends on what you're used to.
The Approach
There is no magic ingredient in Slim Fast that will make you less hungry -- no appetite suppressant supplements, no caffeine or any other fad diet supplement. Slim Fast takes a nutritional approach to satiety instead, relying on slow-digesting macronutrients and a thick consistency to fill you up and keep you full for a longer period of time. The shakes and bars are formulated precisely to maximize satiety-inducing nutrients and minimize empty calories, which is why this diet approach isn't likely to work with just any substitution.
Satiety-Inducers
A single serving of the milk chocolate Slim Fast shake contains 10 g of protein, 6 g of fat and 5 g of fiber. Protein and fat take longer to digest than carbohydrates, so you may feel full longer as the shake slowly works its way through your digestive system. Fiber also increases fullness because it is a bulking agent -- your body cannot digest fiber, so it moves through your system untouched, slowly. A sudden increase in fiber consumption can cause gas and bloating, which also contributes to a feeling of fullness. The smooth, creamy texture of the shake is achieved by incorporating air, which, once swallowed, adds to the gas and bloating caused by the fiber.
Carbohydrates
Each shake contains about 200 calories, and it's the calorie deficit that causes the weight loss. By reducing the carbohydrate content to only 25 g per serving, the makers keep the calorie count down while managing to keep the protein, fat and fiber content high. Carbohydrates are necessary to keep your energy levels steady, but they digest quickly, and can leave you hungry again before your next meal. The main problem with Slim Fast's carbohydrate content is that 18 of those 25 g are pure sugar. It is important for the shake to taste good so you'll keep drinking it, but it may be too much. The American Heart Association recommends limiting daily sugar intake to 24 g per day for women, and 36 g per day for men. Sugar does nothing to reduce appetite -- in fact, sugar-sweetened beverages have been shown to increase appetite.
Bottom Line
You are more likely to experience appetite control with Slim Fast if you are accustomed to eating smaller, lighter meals. If large, heavy meals are more your style, the Slim Fast shake will likely seem paltry in comparison, and appetite control is unlikely. If you regularly eat high amounts of fiber, you may not feel the fullness associated with sudden fiber increase, and may be hungry again sooner. The plan does, however, allow for two snacks per day -- this means you are unlikely to go for more than three hours or so without eating something, which may help keep you from getting hungry between meals. Drinking plenty of water and learning to differentiate between true hunger and cravings will be helpful as well.
References
- Slim Fast: Creamy Milk Chocolate Shake
- Colorado State University Extension: Weight Loss Products and Programs
- American Heart Association: Sugars and Carbohydrates
- BMJ; Randomised Controlled Trial of Four Commercial Weight Loss Programmes in the UK: Initial Findings From the BBC "Diet Trials"; Helen Truby, et al.; June 3, 2006
- "The American Journal of Clinical Nutrition"; Intake of Sugar-Sweetened Beverages and Weight Gain: A Systematic Review; Vasanti Malik, et al.; August 2006
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