Pros & Cons
- Convenient—grab and go
- No math or guesswork
- The shakes and meal bars could be a turnoff
- Same old, same old, meal after meal
Do's & Don'ts
|Weight Loss Short-term|
|Weight Loss Long-term|
|Easy to Follow|
|For Heart Health|
Scores are based on experts' reviews
You’ll drop 1 to 2 pounds weekly.
Losing weight is as simple as restricting calories and portion sizes—and allowing for some variety and structured flexibility. Slim-Fast products (shakes, meal bars, and snack bars) replace your breakfast, lunch, and snacks, so you get the right amount of the right nutrients. But you also prepare a 500-calorie meal each day, so there’s room to enjoy small portions of your favorite foods.
How does the Slim-Fast Diet work?
Your 1,200 calories a day will come from three snacks (half a banana, a pear, or a Slim-Fast Snack Bar, for example), two Slim-Fast meal replacements (a bar or a shake), and one 500-calorie meal you prepare. Slim-Fast is best for people who need to lose about 20 pounds, which should take 8 to 10 weeks; most people are likely to have trouble sticking to the regimen longer than that. Still, many dieters use Slim-Fast products as occasional meal replacements even after losing weight to make maintenance easier.
Will you lose weight?
Research suggests that Slim-Fast is an effective way to lose weight.
- According to a 2006 study published in the British Medical Journal comparing the effectiveness of four commercial weight loss programs in overweight and obese adults, dieters on the Slim-Fast plan lost an average of about 6 pounds over four weeks. That’s about the same degree of initial weight loss experienced by dieters in the study who followed Weight Watchers and Eat Yourself Slim, although less than the 10 pounds lost, on average, by those following Atkins.
- Long-term results are encouraging. In a four-year study published in Obesity Research in 2000, 100 overweight and obese people were split into two groups. One consumed 1,200 to 1,500 calories a day of regular food and the other replaced two meals a day with Slim-Fast products. Over four years, those who followed the Slim-Fast diet lost an average of 8.5 percent of their initial weight compared to 3.3 percent for the other group. If you’re overweight, losing just 5 to 10 percent of your current weight can help stave off some diseases.
- Researchers spent four years following more than 5,000 people with type 2 diabetes; one group used meal replacement products from either Slim-Fast, Glucerna, OPTIFAST, or HMR, and the other group received diabetes support and education. At the end of the study period, those assigned to the meal-replacement group had lost about 8.6 percent of their starting weight, compared to 0.7 percent for the other participants, according to findings published in Diabetes Care in 2007.
Does it have cardiovascular benefits?
Research is scant and the results mixed.
- In a study published in Obesity Research in 2001, researchers found that dieters following the Slim-Fast plan experienced a greater drop in total and LDL cholesterol than those on an American Diabetes Association-customized “exchange plan” involving substitution of foods of similar nutritional value but different types—for example, swapping one serving of a starchy food for an equivalent amount of protein, which will have less effect on blood sugar. After 12 weeks, total cholesterol had dropped by 7.6 percent and LDL cholesterol by 12.6 percent in the Slim-Fast dieters; no significant decreases were seen among those in the exchange-diet plan.
- However, a study published in 2009 in Public Health Nutrition comparing the Atkins diet, Weight Watchers, Eat Yourself Slim, and Slim-Fast found that after 6 months, the levels of LDL cholesterol and triglycerides (both increase the risk of heart disease) in the Slim-Fast dieters were unchanged.
- Among the 5,000 people with type 2 diabetes mentioned above, those who got meal replacements (rather than diabetes support and education) had greater improvements over a four-year period in systolic and diastolic blood pressure, as well as levels of HDL cholesterol and triglycerides. LDL cholesterol improvements were similar in both groups, according to findings published in 2010 in the Archives of Internal Medicine. Meal replacement products could help decrease the risk of cardiovascular events, the researchers said.
Can it prevent or control diabetes?
Some research suggests that Slim-Fast has a direct beneficial effect on insulin and blood sugar, and weight loss is known to help prevent and control diabetes.
- In the 2001 Obesity Research study mentioned above, Slim-Fast dieters, all with type 2 diabetes, experienced about a 25 percent drop in post-meal insulin level and about an 18 percent drop in blood glucose. Nearly 60 percent of participants were able to reduce the number of diabetes medications they took. The researchers described Slim-Fast as a safe and effective way to improve glucose and insulin levels.
- In another study, published in Diabetes Care in 2003, researchers studied 61 overweight or obese people with type 2 diabetes who either followed a standard low-calorie diet or one based on Slim-Fast products. After one year, 26 percent of those on Slim-Fast were taking fewer diabetes medications than when the trial started, compared with 4 percent in the control group.
- In the 2007 Diabetes Care study mentioned in the weight loss section, use of glucose-lowering medicines among participants in the meal replacement group dropped from 86.5 percent to 78.6 percent. That number increased from 86.5 percent to 88.7 percent among those only receiving diabetes support and education.
Are there health risks?
No indications of serious risks or side effects have surfaced.
But Slim-Fast isn’t considered safe for everyone:
- Products are designed around the nutritional needs of those 18 and over. If you’re younger, talk with a doctor before deciding whether Slim-Fast is advisable; young people are still growing and weight-loss diets often aren’t appropriate.
- Women who are pregnant or breast-feeding should talk to a doctor before starting the plan. They need an ample supply of nutrients, and low-calorie diets aren’t always a smart choice.
How well does it conform to accepted dietary guidelines?
Fat. In the 2010 Dietary Guidelines for Americans, the government recommends that 20 to 35 percent of daily calories come from fat. Slim-Fast provides a healthy 30 percent.
Protein. Slim-Fast provides 20 percent of daily calories from protein.
Carbohydrates. The government recommends that carbs supply 45 to 65 percent of daily calories. Slim-Fast is at 50 percent.
Salt. Government guidelines call for a daily maximum of 2,300 milligrams of sodium, or 1,500 milligrams for those 51 and older, African-Americans, and those with hypertension, diabetes, or chronic kidney disease. Slim-Fast products contain anywhere from 55 to 325 milligrams of sodium per serving. Three of the company’s snack bars, one meal bar, and one shake a day—a typical amount—will supply about 560 mg. By preparing one of Slim-Fast’s 500-calorie recipes, it’s possible to meet either of the recommended limits.
Other key nutrients. The 2010 dietary guidelines call these “nutrients of concern” because many Americans get too little of one or more of them:
- Fiber. Slim-Fast recommends between 25 and 35 grams of fiber a day, in line with government guidelines.
- Potassium. According to the 2010 Dietary Guidelines, a sufficient amount of this important nutrient (see daily nutritional snapshot) counters salt’s capacity to raise blood pressure, decreases bone loss, and reduces the risk of developing kidney stones. It’s not that easy to get the recommended daily 4,700 mg. from food. (Bananas are high in potassium, yet you’d have to eat 11 a day.) Most Americans take in far too little. Slim-Fast products offer 140 to 600 mg. per serving; the company suggests loading up on fruit and vegetables to get more. Depending on snack and 500-calorie meal choices, however, dieters may fall short of the recommended amount.
- Calcium. It’s essential not only to build and maintain bones but to make blood vessels and muscles function properly. Many Americans don’t get enough. Women and anyone older than 50 should try especially hard to meet the government’s recommendation of 1,000 mg. to 1,300 mg. Meeting the goal on Slim-Fast is easy: Each shake contains 500 mg. of calcium, and meal bars contain 300 mg.
- Vitamin B-12. Adults should shoot for 2.4 micrograms of this nutrient, which is critical to proper cell metabolism. You shouldn’t have a problem meeting the guidelines on Slim-Fast. Slim-Fast shakes contain 35 percent of the recommended daily amount of vitamin B-12; meal bars contain 20 percent.
- Vitamin D. Adults who don’t get enough sunlight need to meet the government’s 15 microgram recommendation with food or a supplement to lower the risk of bone fractures. Slim-Fast shakes contain 35 percent of the recommended daily amount, while meal bars have 20 percent. And eating just 3 ounces of sockeye salmon for your daily home-cooked meal will provide 20 micrograms of vitamin D, satisfying the requirement.
Supplement recommended? No. Slim-Fast products contain adequate vitamins, minerals, and nutrients for the typical adult. A French Vanilla Shake, for example, contains 35 percent of the daily recommended vitamin A, 35 percent of vitamin D, 100 percent of vitamin C, and 50 percent of recommended calcium. In a study published in the Journal of Nutrition in 2004, researchers split 66 overweight and obese Australians into two groups: One consumed two Slim-Fast meal replacement products and one low-fat meal each day, and the other group followed their own low-fat, low-calorie diet. The Slim-Fast dieters consumed more magnesium, calcium, iron, and zinc than the other group (but less dietary fiber).
How easy is it to follow?
Depends on how long you want to dine on Slim-Fast shakes, snack bars, and meal bars. There’s a wide variety of flavors, but if you don’t like the taste, the diet isn’t for you; you’re allowed only one home-cooked meal a day.
Meals and snacks are as easy as grabbing a can or a bar. Alcohol is discouraged but not prohibited, and restaurants are OK as a source of the one non-Slim-Fast meal a day. The company’s online resources may be helpful.
Recipes. Slim-Fast provides hundreds of recipes for the 500-calorie meal dieters get to eat each day. Choices range from Asian beef salad, to fish tacos with bell pepper slaw, to cheeseburgers.
Eating out. Allowed. If you’re replacing a Slim-Fast meal bar or shake with a restaurant meal, try to stick to 300 calories for lunch, and 500 to 600 for dinner. Slim-Fast provides dining-out tips. Grilled or roasted entrees are recommended, with steamed vegetables on the side, and request dressing and sauce on the side.
Alcohol. Slim-Fast recommends eliminating alcohol, though having a drink once in a while is OK. Opt for a 6-ounce glass of wine (140 to 160 calories) rather than a margarita (possibly more than 500 calories). Or go for a shot of hard liquor (70 to 90 calories) mixed with a calorie-free beverage.
Timesavers. The diet itself is a timesaver. Shakes, meal bars, and snack bars are all grab-and-go; you only need to think about preparing one meal a day.
Extras. Log onto slim-fast.com to calculate your body mass index and figure out how much weight you can reasonably expect to lose over a certain period. Chat with fellow dieters via message boards. Slim-Fast’s registered dietitian responds to questions, too, and the company interacts with dieters on its Facebook page.
Nutrition experts emphasize the importance of satiety, the satisfied feeling that you’ve had enough. According to the company, the protein and fiber content of a Slim-Fast meal replacement can quell hunger for up to four hours.
Slim-Fast’s products come in an array of flavors—chocolate mint and peanut butter crunch snack bars. Chocolate cookie dough, fudge brownie, and fruit and yogurt trail mix meal bars. Cappuccino delight, French vanilla, and strawberries and cream shakes. But consuming up to five Slim-Fast products a day could get old fast.
How much does it cost?
A 24-pack of shakes runs about $35, 24 snack bars about $17. You can order online at sources like amazon.com and drugstore.com, or buy the products at most grocery and convenience stores. Free online registration allows access to hundreds of recipes, plus tools like meal and activity trackers.
Does the diet allow for restrictions and preferences?
Customizing Slim-Fast can be tricky—pick a preference for more information.
Vegetarians can proceed with the plan by following Slim-Fast’s suggestion of a 4- to 6-ounce meat alternative, such as quinoa or tofu, with your 500-calorie meal. Products contain dairy and are unsuitable for vegans.
No gluten-free products.
No specific low-sodium meal plan. You’ll have to check out each product for salt content. A Chocolate Mint Snack Bar, for example, has 65 milligrams of sodium, while a Chocolate Peanut Caramel Meal Bar has 320 mg. Most shakes contain 200 to 220 mg. You can also opt for Slim-Fast Shake Powder and prepare the mix with low-sodium milk, which has about 10 mg. of sodium per 8 ounces compared to 130 mg. in regular milk.
Many products are kosher—check the front label for the OU (Orthodox Union) symbol.
No products are certified as Halal, but they contain no animal products other than cow’s milk.
What is the role of exercise?
Strongly encouraged. Slim-fast recommends at least 30 minutes of physical activity a day most days of the week, but it need not be strenuous—three 10-minute walks will do the job.
Last updated by Angela Haupt | January 02, 2013
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