According to Good Housekeeping, the liquid diet drink trend began in the early 1930’s, with “Dr. Stoll’s Diet-Aid, the Natural Reducing Food.” This low-calorie product, a combination of milk chocolate, starch, whole wheat, and bran, mixed with water to create drinks that replaced breakfast and lunch (http://homearts.com/gh/health/07nutrb2.htm). Since then, numerous liquid products and other diet-aid derivatives have entered the market promising to shed weight and encouraging healthy lifestyles. A leading brand name on today’s market that makes such claims is Slim-Fast®.
“The Slim-Fast® Foods Company is dedicated to the advancement of nutrition for good health” (http://www.slimfast.com/company/company.asp). The company is “committed to the development of wholesome and balanced nutritional products to aid in weight management and improved health” (http://www.slimfast.com/company/company.asp). Slim-Fast® offers a full line of ready-to-drink shakes, powders, Ultra Slim-Fast® Nutritional Snack Bars, Slim-Fast® Breakfast and Lunch Bars, and Slim-Fast® Meal On-the-Go Bars to assist in weight loss, weight maintenance, and the development of healthy eating habits.
Body mass index (BMI) refers to the percentage of body fat; it is the weight of an individual divided by their squared height. A BMI between 24 and 30 is considered overweight for women, a BMI between 25 and 30 is considered overweight for men, and a BMI greater than 30 is considered obese for both sexes (Kaplan, Sallis, and Patterson, page 397).
Exercise is a subset of physical activity that involves bodily movement but is planned, structured, and done repetitively to improve and maintain one or more components of fitness (Kaplan, Sallis, and Patterson, page 369).
Resting metabolic rate (RMR) is the rate at which calories are burned when a person sitting quietly at rest (Kaplan, Sallis, and Patterson, page 415).
Crawford and Campbell (1999) found that common definitions of weight differ drastically from medically accepted BMI values. In this study, 1342 participants (666 men and 676 women) completed surveys in which they defined ideal weight and the term ‘overweight.’ The average BMI value that women considered ideal was 22.7 and the average ideal BMI value for men was 24.9. Medically, a BMI value of 25 is considered overweight. In the study, however, women defined an average BMI value of 23.7 as overweight and men defined an average BMI value of 26.1 as overweight. The BMI values for ideal weight and overweight increased in both sexes with the participants’ ages and current weights.
In summary, men and women often do not have realistic images of their ideal weight and/or being overweight. This fact can create a problem when men and women strive for unrealistic weight goals.
The Slim-Fast® Company proposes a comprehensive plan for weight loss and weight maintenance. The Plan for weight loss consists of replacing two meals with Slim-Fast® shakes, eating one sensible meal, and eating three healthy snacks each day. For weight maintenance, the Plan includes replacing one meal with a Slim-Fast® shake, eating two sensible meals, and eating three healthy snacks each day. In the event of weight gain, the company recommends restarting the weight-loss portion of the Plan for as long as necessary to again reach an optimum weight (http://www.slimfast.com/plan/plan.asp).
The Slim-Fast® Foods Company offers the most comprehensive representation of its products at its official website (http://www.slimfast.com). However, the website does not provide a way to order Slim-Fast® products. Thus, the Slim-Fast® Foods Company recognizes that their product alone cannot provide adequate nutrition or healthfully decrease weight. Although the company is looking to make money from selling its products, it also exhibits a genuine interest in helping people lose weight and maintain healthy lifestyles.
On the other hand, several websites, such as http://buyinprivate.site.yahoo.net/buyinprivate/jumstardietp.htm, http://st2.yahoo.net/moreonline/grocery-diet-aids-diet-aids---powder.html, and http://www.marciaschs.com/p0000105.htm, offer ways to purchase Slim-Fast® and other weight-loss and nutritional products, but offer little or no information about these products. Thus, these companies strive solely to sell the product and make money. Slim-Fast® products are also readily available at most grocery, drug, and health food stores.
The Slim-Fast® Foods Company website features advice about numerous dietary strategies and tips for success. For example, the company stresses the importance of counting calories as part of a comprehensive weight-loss plan. The company claims, “Most people consume more calories than they should each day” (http://www.slimfast.com/plan/counting.asp); however, the site offers no support of this claim. The company also claims that an individual should cut 500 calories per day from his or her diet to lose weight at a rate of one pound per week. Again, the site offers no evidence that this information is accurate or that this rate of weight loss is safe. However, the claims are valid, as the FDA considers dropping 300 to 500 calories per day from a current calorie intake effective to safely lose one to two pounds per week (Department of Health and Human Services, 1996).
The site also features common advice about healthy snacking (http://www.slimfast.com/plan/snacking.asp) and portion sizes (http://www.slimfast.com/plan/portion.asp). It provides an example of a typical daily menu (http://www.slimfast.com/plan/7daymenu.asp), healthy recipes (http://www.slimfast.com/plan/menu.asp), and cooking advice (http://www.slimfast.com/success/easy.asp).
The company stresses realistic goal setting and expectations. The website claims that “For an initial weight-loss goal, many health experts suggest 10% of your current body weight” (http://www.slimfast.com/plan/plangoal.asp). However, the company offers no evidence in support of this claim and does not recognize the specific “health experts” who make this suggestion. As mentioned earlier, under Common Views of Weight, men and women often do not have realistic views of ideal weight. Thus, this advice may prove difficult to follow. The site also considers the helpfulness of a positive attitude (http://www.slimfast.com/success/power.asp) and of having a weight-loss partner (http://www.slimfast.com/success/connect.asp), but again offers no support of this advice.
The company also stresses the importance of exercise as part of a comprehensive weight-loss and weight-maintenance plan plan. The web site claims, “Aside from changing the way you eat, exercise is the most important step you can take to help you lose weight and improve your health. People who include physical activity in their weight-loss programs are more likely to keep the weight off than are people who ONLY make dietary changes. Any increase from your usual activity level helps you burn calories, firm up, and improve your health” (http://www.slimfast.com/success/fit.asp). However, the site does not offer any evidence to support the claims. Scroll down this page to read more about exercise and weight loss, under Exercise.
The website also presents common lifestyle tips for successful weight loss and healthy eating habits (http://www.slimfast.com/success/life.asp), such as identifying vulnerable over-eating situations, avoiding temptations, and shopping tips. Scroll down this page to read more about planned grocery shopping, under Shop With a List.
Something to think about: When farmers fatten up animals to sell, what do they do? Well, for one, the farmers coop up the animals, limiting their physical activity (Zachwieja, 1996). Hmm.
Several review papers that summarize studies concerning exercise and weight loss stress the same points. First, the addition of physical activity to a calorie-restricted diet produces better weight loss results and weight maintenance success than a calorie-restriction diet alone. Second, physical activity may create a more favorable body composition than a calorie-restricted diet. Calorie-restricted diets often burn lean body mass, whereas physical activity burns fat while promoting lean body mass. Third, an energy expenditure of at least 1500 calories per week is sufficient to maintain weight loss. Fourth, exercise has benefits other than weight loss, such as lowering rates of morbidity and mortality, increasing resting metabolic rate, lowering blood pressure, improving cardiovascular function, and reducing cholesterol levels. Thus, these review papers support the claims about the importance of exercise in weight loss and weight maintenance made by the Slim-Fast® Company.
In a prospective study by Beneke, Davis, and Vandertuig (1988), a group of women planned their families’ meals for the week, transferred the ingredients needed to a grocery list, and organized the list according to the layout of their grocery store. This study showed that the planned shopping with a list helped to reduce weekly food purchases, including spontaneous purchases of high-fat, attractive foods, as compared to a group of women who did not plan their shopping. The study also showed that the decrease in food purchased often corresponded with weight loss. Thus, this study supports the advice offered by the Slim-Fast® web page about planned shopping.
Is the Plan Effective?
The Slim-Fast® web page showcases the testimonials of four individuals, each who lost miraculous amounts of weight and lead amazingly healthy and energetic lives by following the Slim-Fast® Plan (http://www.slimfast.com/testimonials/testimonials.asp). Interestingly, each testimonial ends with the statement “Results not typical.” In the question portion of the site, the company states that “Clinical studies show that weight loss varies with the individual and averages 1 to 2 pounds per week” (http://www.slimfast.com/qa/average.asp). Relatedly, several individuals have posted Slim-Fast® success stories on the Internet at sites such as http://www.physical.com/jchatter/messages. Scroll down this page to read more about the evidence supporting and debunking these claims, under A Study Supporting Slim-Fast, Another Study Supporting Slim-Fast, and A Study of the Maintenance of Weight Loss.
Slim-Fast® claims “Randomized clinical trials show that patients who follow the Slim-Fast® Plan lose more weight than those on standard diets and they keep the weight off” (http://www.slimfast.com/medical/medical.asp). The Slim-Fast® web page offers proof of their claims in the form of two clinical studies, summarized at http://www.slimfast.com/medical/m_ditsch.asp and at http://www.slimfast.com/medical/heber.asp. Scroll down this page for more complete analyses of these studies, under A Study Supporting Slim-Fast® and Another Study Supporting Slim-Fast® and for an additional study of weight maintenance, under A Study of the Maintenance of Weight Loss. In summary, the Slim-Fast® Company offers sound evidence to support their weight-loss claims.
Ditschuneit, Flechtner-Mors, Johnson, and Adler (1999) found that meal replacements such as Slim-Fast® are effective in long-term weight loss and weight maintenance. Their study had two phases. The first phase was a prospective study that lasted three months and compared two diet plans to determine which produced better weight loss results, as described below. The second phase lasted two years and studied the maintenance of one diet plan, also described below. The 100 participants in this study were men and women over the age of 18 with body mass indexes between 25 and 40 who were dissatisfied with previous calorie-restriction diets. Prior to phase 1 of the study, the participants were randomly assigned to either group A, which contained 41 female and 9 male participants, or group B, which contained 38 female and 12 male participants. All participants received monthly instruction and feedback from a nutritionist concerning food choices, meal planning, portion sizes, and the construction of a food diary. During both phases, both groups were instructed to eat three meals and two snacks daily. Participants in group A selected their own meals and snacks from regular food. Participants in group B, however, replaced two meals and both snacks with Slim-Fast® products. In phase 2 of the study, both groups replaced one meal and one snack with Slim-Fast® products. Participants reported monthly for weighing and measuring.
At the end of phase 1, men in group A lost 1.1 + 2.6 kg, men in group B lost 8.4 + 3.9 kg, women in group A lost 1.2 + 2.1 kg, and women in group B lost 6.8 + 3.3 kg. At the end of phase 2, both groups lost weight at approximately the same rate. At the end of the study, group A had lost 5.9 + 5.0% of their original body weight and group B had lost 11.3 + 6.8% of their original body weight. A total of 37 participants dropped out of the study for various reasons, but this did not significantly affect the results of the study. This study also addressed the decrease of certain risk factors for disease, such as blood pressure and cholesterol, that accompany weight loss. In summary, this study supports the claims that Slim-Fast® products are effective in initial weight loss and in weight maintenance.
Heber, Ashley, Wang, and Elashoff (1994) found that continued use of a meal replacement, such as Slim-Fast is an effective way to lose weight and maintain long-term weight loss. They also found Slim-Fast® to be effective in initial weight loss. This study actually addressed the entire Slim-Fast® Plan, as a low-fat diet accompanied the use of the products. The prospective study took place in two time frames: an initial 12-week weight-loss period and a subsequent 104-week maintenance period. The participants in this study were 71 mildly obese males with an average age of 38.7 years and an average of 119% of ideal body weight and 230 mildly obese females with an average age of 38.3 years and an average of 122% of ideal body weight. Participants received minimal nutritional information and feedback during the study. During the initial weight-loss period, participants were instructed to replace two meals with Ultra Slim-Fast® products and to eat one balanced meal, for a total of 1000-1200 calories daily. The participants reported weekly for weighing and rated the taste, appetite satisfaction, convenience, overall rating, general well-being, and energy level of the weight loss program. After the first 12 weeks, 35 participants who lost less than nine pounds during the first time frame were considered non-adherent and were excluded from the study. During the second time frame, the remaining participants replaced one meal per day with a Slim-Fast® product and ate two well-balanced meals to lose weight or maintain their desired weight. The participants reported bi-weekly for weighing.
273 participants remained in the study for the first time frame. At the end of the 12-week time period, the men in the study lost 18.6 + 7.0 pounds and reduced their percentage of ideal body weight to 108 + 5%. The women in the study lost 14.0 + 6.5 pounds and reduced their percentage of ideal body weight to 111 + 7%. A significant number, 44.1%, of participants dropped out or were excluded from the study during the second time frame. After one year, 184 participants remained in the study: 41% of the participants weighed less than their 12-week weight, 67% of the participants kept 80% of their weight loss off, 22% of the participants kept a portion (below 80%) of their weight loss off, and only 0.5% of the participants weighed more than their original weight. After two years, 136 participants remained in the study: 22.8% of the participants weighed less than their 12-week weight, 39% of the participants kept 80% of their weight loss off, 30.9% kept a portion (below 80%) of their weight loss off, and 7.4% of the participants weighed more than their original weight. The weight loss also provided benefits, such as lowering cholesterol levels. In summary, this study supports the claims that Slim-Fast® products are effective in initial weight loss and in weight maintenance, even in self-directed programs.
McGuire, Wing, Klem, Seagle, and Hill (1998) studied the weight-loss maintenance techniques of 893 people, 81% female and 19% male, who had lost weight on their own (447 participants), through organized programs (313 participants), or with a liquid diet-aid (133 participants). The participants were members of the National Weight Control Registry (NWCR), over the age of 18, had lost over 30 pounds, and had kept the weight off for at least one year. Through questionnaires, the researchers gathered background data from the participants: current height, current weight, maximum lifetime weight, amount of weight cycling, and disease history. The questionnaires also gathered information concerning the recent weight loss that qualified the individual for the study: time taken to lose the weight, a reference physician to prove the weight loss, and motivation for the weight loss (medical, emotional, or life events). The participants rated the perceived level of difficulty of losing the weight and the level of difficulty of maintaining the weight loss on a scale of one to seven. Further questions determined the dietary strategies that the participants used for their weight-loss maintenance: counting calories, counting fat grams, limiting calories from fat, limiting quantity of food eaten, limiting certain foods, limiting certain groups of food, using a liquid diet-aid, using a structured diet or program, and frequency of weighing. A Block Food Frequency Questionnaire (BFFQ) detailed the dietary energy intake from fat, carbohydrates, and proteins. An Eating Inventory further assessed dieting behavior. A Paffenbarger Activity Questionnaire (PAQ) determined weekly calorie expenditure to exercise.
The On Own group had greater difficulty in losing the weight, mostly likely due to the lack of professional instruction, and reported the least difficulty in maintaining the weight loss. The On Own group used exercise to maintain weight loss and rarely used dietary strategies. The Liquid Diet group had the most medical problems and lost the most amount of weight, but were still the heaviest individuals in the study and had the most medical problems. The Liquid Diet group used dietary strategies, such as counting calories, limiting fat, and using a liquid diet aid, to maintain weight loss, but reported the most difficulty maintaining the weight loss. In summary, this study recognizes that a liquid meal replacement is effective in treating obese patients, thus supporting the claims made by the Slim-Fast® Company. However, this study also notes the extreme importance of physical activity in maintaining weight loss.
In conclusion, the comprehensive Slim-Fast® Plan, including meal replacement, healthy eating, and exercise, is an effective method to lose weight and maintain weight loss. Thus, the weight-loss claims found on the Slim-Fast® web page are valid and the Slim-Fast® site is a valuable tool for information concerning weight loss.
Psychology DepartmentThe Health Psychology Home Page is produced and maintained by David Schlundt, PhD.
Vanderbilt Homepage | Introduction to Vanderbilt | Admissions | Colleges & Schools | Research Centers | News & Media Information | People at Vanderbilt | Libraries | Administrative Departments | Medical
|Return to the Health Psychology Home Page|
|Send E-mail comments or questions to Dr. Schlundt|