Weight Loss, Diets, and Supplements: Does Anything Work?

The past 50 years have seen a proliferation of diets. These have ranged from total fasting, to consuming 300–400 calories/day of liquid supplements, to eating 1,200–2,100 calories/day with varying macronutrient distributions (5–60% carbohydrate, 2–70% fat, and ≥20% protein).6 

Our patients who are concerned about their weight may have tried one, two, or more of these diets in an effort to lose or manage their weight. In the past decade, as Americans have become heavier, the diet industry has exploded. Of the top 50 best-selling diet books, 88% have been published since 1997.7 

Because of the growing popularity of fad diets, the U.S. Department of Agriculture (USDA) initiated a research program to assess the health and nutrition effects of popular diets. One of its first activities was a comprehensive, evidence-based literature review. In January 2001, the USDA posted an article on its Website8 summarizing this review, and later published the article in Obesity Research.7 

Although the USDA literature review was not specifically focused on weight loss and diabetes, it did provide information for health care professionals to use when counseling patients with diabetes. Table 1 offers evidence statements and evidence ratings from the review. This literature review confirmed that all low-calorie diets—and calorie reduction is the hidden foundation of most of the popular diets—result in loss of body weight and body fat. However, some diets are more nutritionally adequate than others.

The USDA’s second step was to analyze existing data to determine the association between different health and nutrition indicators and popular diets.9 The USDA reviewed data collected between 1994 and 1996 from more than 10,014 adults aged 19 years and older as part of the Continuing Survey of Food Intake by Individuals (CSFII). The CSFII consists of food consumption and dietary pattern information on a nationally representative sample.

Popular diets were categorized into three prototypes and reviewed for total energy intake, macronutrient distribution, healthy eating index (HEI; range 0–100), fruit score (range 0–10), and variety score (range 0–10). A brief summary of results is shown in Table 2. Although these data do not show cause and effect, they do suggest that people eating low- to moderate-fat diets are more likely to eat fewer calories and a more nutritionally balanced diet (the higher the HEI, fruit, and variety scores, the more nutritionally balanced the diet).

In addition to diets, many patients are trying dietary supplements as a means of achieving quick weight loss. Under the Dietary Supplement Health and Education Act (DSHEA), a dietary supplement is defined as a product other than tobacco that contains a “dietary ingredient” and is intended to supplement the diet. Dietary ingredients include vitamins, minerals, herbs or other botanicals, amino acids, and substances such as enzymes, organ tissues, and metabolites. Dietary supplements must be labeled as such and can come in many forms, including powder, tablet, liquid, or capsule. They should not be used as a conventional food or as a sole meal or diet.10 

Dietary supplements can play an important role in health promotion and the prevention of chronic disease.10 However, concerns over their safety, dose, and advertising must be considered. A primary concern is that DSHEA does not require pre-market safety approvals for dietary supplements. Manufacturers are not required to disclose any information they have about the safety or alleged benefits of their supplement products.10 In one example, animal studies showed promise for the supplement hydroxycitrate, the active compound found in the Garcinia cambogia plant. However, a human trial11 found no benefit for weight loss. Nevertheless, hydroxycitrate is still being promoted for weight loss based on the animal studies.

Another concern is that dietary supplements may be described as “natural” or even “drug-free,” in advertising. Some patients may interpret this to mean that there are no safety concerns associated with the use of these products. Metabolife 356, for example, is marketed as a dietary supplement but contains ephedrine derived from the herb ma Huang and caffeine from the herb guarana. Ephedrine and caffeine are technically drugs, but when used in a dietary supplement, they are classified as herbs. Although controversial, there are safety concerns for ephedrine and even greater concerns when it is combined with caffeine. The Food and Drug Administration has proposed labeling changes for dietary supplements containing ephedrine alkaloids and has suggested limiting the dose per tablet because of several reports of adverse reactions and deaths associated with its use.12 

Additional concern related to dietary supplements is the lack of congruency between doses and forms of products used in studies and those shown on the label of the supplement product. In the case of the dietary supplement pyruvate, for example, the dosage used in weight-loss studies ranged from 25 to 30 g/day. The typical dose found in products sold in health food stores and through mail-order companies contains only 400–600 mg pyruvate per capsule, with recommendations to take 2–3 capsules 2–3 times daily, which translates into 2.4–3.6 g/day.13 

Because many patients choose to self-medicate with dietary supplements for weight loss despite the controversy and lack of evidence supporting their use, it is imperative for health care professionals to be aware of the safety concerns associated with weight-loss supplements. A selection of popular supplements and their associated safety concerns are presented in Table 3.14–22 

Evidence suggests that low- and moderate-fat, calorie-restricted diets promote weight loss and are more nutritionally adequate than high-protein, high-fat, low-carbohydrate diets. Evidence is lacking to support the inclusion of high-protein, high-fat, low-carbohydrate diets or weight-loss supplements in weight management programs.

Behavioral weight-loss programs that focus on calorie balancing, using a combination of decreased caloric intake and increased exercise, are shown to be the most effective approaches to weight loss. Such programs typically include a caloric goal of 1,200–1,500/day, which is designed to produce an energy deficit of 500–1,000 calories/day and consequently a 1- to 2-lb/week loss. In addition, they advocate consuming 20–25% of total calories from fat and expending a minimum of 1,000 calories/week23 and optimally 2,000 calories/week24 through exercise. Additionally, many successful programs offer education and guidelines for stimulus control; self-monitoring (i.e., regular weighing, logging food intake); restaurant and social eating; healthy food choices and portion control; stress management; modest goal setting; self-talk;23,25 problem solving; recipe modification; assertiveness training;24 and motivation enhancement.23,26 

People participating in behavioral weight-loss programs lose an average of 8.4 kg (18.5 lb) during treatment (∼20 weeks) and are able to maintain, on average, two-thirds of this loss 9–10 months after initial treatment.27 However, within 3–5 years after treatment, they gradually return to their baseline weight.4,27 

Although this sounds discouraging, some individuals have used effective strategies to maintain their weight loss over the long term. The National Weight Control Registry (NWCR) provides the largest collection of data on successful weight losers and maintainers. Participants eligible for enrollment in the registry must have lost ≥30 lb (13.6 kg) and have maintained the loss for ≥1 year.28 More than 3,000 people are enrolled in the registry.29 

A total of 629 women and 155 men from the registry were surveyed to identify strategies they used to successfully lose and maintain weight.28 Participants in the study lost an average of 66 lb and maintained the minimum required weight loss (30 lb) for an average of 5.5 years. Sixteen percent of the sample maintained the 30-lb weight loss for ≥10 years. More than half (55%) of the sample sought formal or professional assistance for weight loss (e.g., Weight Watchers or sessions with a registered dietitian), whereas the remaining 45% lost weight on their own.

To facilitate weight loss, 89% modified both dietary and activity habits; 10% modified diet only; and 1% modified activity only. Of those who made dietary changes, the three most frequently used methods were limiting certain types of food or food groups (87.6%), decreasing portion sizes (44.2%), and counting calories (43.7%). In addition to dietary changes, physical activity and exercise were influential in participants’ weight-loss efforts. Ninety-two percent of the participants exercised at home, and about one-third exercised with a group (31.3%) or a friend (40.3%). Women were more likely to report participating in walking and aerobic dancing, and men were more likely to participate in competitive sports and weight lifting.

Weight maintenance strategies used by registry participants were similar to those used for weight loss. A summary of these strategies is shown in Table 4. Strategies used by NWCR participants to lose and maintain weight are comparable to typical behavioral weight-loss interventions. Participants followed a low-fat (∼25% of total calories) and low-calorie diet, practiced self-monitoring techniques (e.g., self-weighing), modified portion sizes, and expended >2,000 calories/week through physical activity and exercise.

Strategies used to promote weight loss and weight maintenance are similar to strategies used for improving blood glucose control. Individuals with diabetes do benefit from improving food choices, spacing food intake throughout the day, reducing calories, and exercising regularly—all strategies necessary for weight management.28–30 However, it is important to frame weight management goals with diabetes management goals. Often, when patients are diagnosed with type 2 diabetes, they are advised to lose weight to “avoid medication”; weight loss becomes a primary treatment goal.

Should weight loss be a primary treatment goal? How long should you hold off medication to see if weight loss will improve glycemic control? These are important questions for health care professionals to consider when recommending weight loss to individuals with diabetes.

While weight loss has been shown to improve glycemic control in most people, it does not do so in all individuals with diabetes.32–35 In general, the greater the fasting plasma glucose (FPG), the greater the weight loss required to return FPG to a normal range.32 Most individuals newly diagnosed with diabetes will respond to a 5- to 7-kg (11- to 15.4-lb) weight loss.32 However, if the initial FPG is >252 mg/dl, for example, a significant and most likely unrealistic weight loss would be required to achieve normal FPG levels.

Even when an individual with diabetes diets sufficiently for 3 months to lose weight and reduces FPG to <108 mg/dl, this level of control is usually only maintained when energy intake continues to be restricted and more weight is lost. If the diet is restricted only sufficiently to maintain the initial weight loss, the FPG increases. Thus, reduction of energy intake is as important as losing weight and maintaining the weight loss if lowered FPG levels are to be maintained.32 This same trend was observed in another study,34 which showed that improvement in glycemic control for a given weight loss is greater initially than at 1 year.

The American Diabetes Association position statement on Nutrition Recommendations and Principles for People with Diabetes Mellitus35 emphasizes the importance of improving the metabolic abnormalities associated with diabetes—hyperglycemia, dyslipidemias, and hypertension. Although weight loss is one of several strategies that can help improve metabolic abnormalities, it should not be the primary focus.35 

Type 2 diabetes is a progressive disorder, and as a result, therapy needs to be intensified over time.32 We should help patients understand and accept that, although weight loss and energy restriction may initially help them improve their diabetes control and even temporarily avoid oral agents or insulin, they may still require medication in the future. When the pancreas fails, diet therapy alone will not be enough, and medication will be needed to achieve blood glucose control.32 

What do we need to know as health care professionals, and what should we say to support our patients’ weight management efforts while helping them achieve their diabetes management goals? First, explain to patients that weight management is not the primary focus of their diabetes management plan. Second, review their weight-loss expectations and goals. It is important to help patients establish realistic expectations and to provide them with support. Successful weight management is possible, but it is a lifelong process requiring the same level of commitment as diabetes management. Third, educate patients about popular diets and supplements as they emerge. Encourage them to resist the avoid the temptation to buy a “magic” pill or potion that promises effortless weight loss or weight maintenance. Table 5 offers additional patient education messages and counseling strategies.

It is our responsibility as health care professionals to stay abreast of the latest fad diets and dietary supplements so that we can effectively educate and inform our patients about their potential benefits and risks. Additional long-term and comprehensive weight management programs must be developed to deal with the epidemic of obesity and diabetes.