Popular Diets: Examining Weight Loss Diets for Geriatric Patients

This is the third article in a continuing series on nutrition in the elderly. The first two articles in the series, “Vitamin D and Calcium: Implications for Healthy Aging,” and “Vitamin B₁₂: Considerations for Maintaining Optimum Health in Elders” were published in previous issues of Clinical Geriatrics^®. The final article, to be published in an upcoming issue, will discuss nutritional assessment of the geriatric patient.
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Advancing age is associated with a slower metabolic rate, declines in muscle and bone mass, reduced total body water, and a relative increase in body fat deposition, particularly of intra-abdominal fat.¹ Although these factors sometimes contribute to undesirable or excessive weight loss, a growing proportion of older adults are overweight or obese, which predisposes them to several debilitating health conditions and is associated with frailty.² Frailty hinders physical activity and independence and impairs quality of life. Proper diet and exercise are important for overall health and may prolong self-sufficiency in older adults. Physicians should therefore be prepared to advise elderly patients who wish to maintain the highest quality of life with respect to achieving an optimum balance of energy and nutrients, how to avoid excess fat accumulation and weight gain, and additional efforts they can take to preserve their well-being.

Determining the optimum approach to weight control can be challenging. The obesity epidemic fuels a multibillion-dollar diet industry, and patients may seek guidance from healthcare providers with questions regarding a variety of diets and weight loss regimens they have seen or heard about from friends, family, or other sources. These highly marketed weight loss plans make numerous promises, and it is important that physicians and patients know how to evaluate their strengths and weaknesses and select a dietary plan that the patient can maintain and is most likely to promote a lifetime of good health. An important first step in making the proper recommendation is being aware of the tenets shared by the most popular weight loss plans.

We provide an overview of some of the most popular weight loss diets (Table 1) and describe the risks and benefits of these plans for older adults; however, regardless of which plan is selected, every effort should be made to minimize muscle and bone loss. Because exercise can help individuals maintain bone and muscle balance, it should be stressed as an integral component of any weight loss plan.

Key Considerations

Physicians and patients should be cautious of diets that promote quick weight loss, claim to be a cure-all, encourage or require the use of supplements, have strict rules on what and when to eat, discourage or completely avoid certain food groups, and are touted as a short-term “fix.”³ Short-term interventions may not be designed to promote health over time, and patients should be encouraged to adopt eating behaviors that will result in long-term good health and weight control.

Weight loss should be achieved gradually and weight maintained over time.  A pound of body fat stores 3500 kilocalories. To achieve weight loss at a rate of approximately 4 to 10 lb per month, adults are advised to reduce daily energy intake or increase daily energy expenditure by 500 kilocalories daily. The US Department of Agriculture’s current dietary guidelines for Americans recommend eating nutrient-dense foods, avoiding trans fats, limiting consumption of refined grains, and, for adults 51 years and older, limiting sodium intake to 1500 mg daily.⁴ Nutrient-dense foods include fruits, vegetables, whole grains, nuts, lentils, dry beans, liquid vegetable and fish oils, lean meat, fish, and reduced-fat dairy products. For the average healthy older adult, approximately 45% to 65% of total energy intake should come from complex carbohydrates, 10% to 35% from lean protein, and approximately 20% to 35% from fats.⁴ Maintaining adequate intake of fiber and fluid is especially important for older adults, as is ensuring adequate intake of B vitamins, calcium, and vitamin D. What follows is an overview of several food-based diets as well as two supplement-supported diets.

Mediterranean and DASH Diets
Two plans that promote the aforementioned desirable ratio of nutrients for older adults are the Mediterranean diet and the Dietary Approaches to Stop Hypertension (DASH)⁵ diet. These diets have fruits, vegetables, whole grains, and legumes as dietary staples. The Mediterranean diet promotes generous consumption of whole grains, legumes, and dry beans; moderate intake of dairy and alcohol; and very limited consumption of red meat. Olive oil serves as the main source of lipids. Studies have associated the Mediterranean diet with lower incidences of Parkinson’s disease, Alzheimer’s disease, and diabetes, and a decreased mortality from all causes, specifically a reduction in deaths from cardiovascular events and cancer.⁶ The DASH plan encourages consumption of low-fat dairy products and lean meats and has been associated with lower blood pressure and reduced rates of cancer,⁷ diabetes,⁸ and osteoporosis.⁹

Carbohydrate-modified Diets
Diets that are low-carbohydrate/high-protein (LC/HP) are among the most popular weight loss plans. It is thought that LC/HP diets achieve weight loss through inducing ketosis and short-term diuresis. Ketone bodies are prodduced when glucose is scarce, causing the body to turn to stored fat as the primary energy source. Although many tissues can use ketones as fuel, the brain requires glucose. Therefore, long-term adherence to ketogenic diets should be discouraged. Common LC/HP plans are Atkins,¹⁰ the Zone,¹¹ Sugar Busters!,¹² and the South Beach Diet.¹³

The Atkins diet consists of four phases, with each phase allowing a progressively higher carbohydrate intake. The original Atkins diet permitted adherents to eat unlimited amounts of fat and protein, while limiting carbohydrates to less than 50 g daily. A 2010 update, referred to as the “New Atkins Diet,” limits protein intake to 4 to 6 oz with each meal and encourages greater vegetable consumption.¹⁴ The Atkins diet notes that the initial phase has a diuretic effect, resulting in dramatic shifts in fluid, electrolytes, and salt, which could be a concern for older adults.¹⁴

The South Beach Diet is similar to the Atkins plan, guiding dieters through carbohydrate-restricted phases to reach weight goals. Unlike Atkins, which places no restrictions on fats, the South Beach Diet calls for substituting polyunsaturated and monosaturated fats for saturated fats. The first phase of the diet limits carbohydrate intake to less than 50 g daily and prohibits alcohol. The second phase is slightly less restrictive and is meant to be followed until the desired weight is achieved. Phase three is a weight maintenance plan that allows the dieter to eat more carbohydrate-containing foods.

The Zone is based on its founder’s theory that eating too many carbohydrates leads to insulin resistance and body fat deposition and that certain proteins can reduce hunger. Zone dieters are encouraged to purchase patented products that claim to burn fat faster and reduce inflammation.

Sugar Busters! centers on the concept that eating too much sugar causes weight gain. The diet recommends foods that are low on the glycemic index, encouraging dieters to eat high-fiber vegetables and whole grains. The glycemic index scores each food according to how it affects postprandial glucose levels in normal individuals—the higher the glycemic index, the higher the potential postprandial glucose response.

In general, LC/HP diets may be deficient in fiber, B vitamins, calcium, and potassium. If the diet is low in fruit and vegetables, it may be deficient in biologically active compounds such as polyphenols, which have antioxidant properties and help regulate pathways that prevent cell damage. High-protein diets may increase the kidneys’ acid burden, causing higher levels of calcium to be excreted in the urine and increasing the risk of nephrolithiasis and osteoporosis.¹⁵ In a study of rats with reduced renal mass, Hostetter and colleagues¹⁶ found that long-term feeding with a high-protein diet (40% of total energy) accelerated nephrosclerosis and proteinuria. Initial weight loss with LC/HP diets tends to be rapid primarily due to glycogen depletion, and diets low in carbohydrates have been found to lower the level of plasma triglycerides and raise the level of high-density lipoprotein (HDL) cholesterol.¹⁷ Because high-fat foods and proteins promote satiety, some dieters may prefer LC/HP diets.

Low-fat Diets
Low-fat diets rely on the premise that reducing one’s intake of fat contributes to a decrease in overall caloric intake. The Pritikin¹⁸ and Ornish¹⁹ diets are examples of dietary plans that are very low in fat, requiring that dieters receive no more than 10% of their daily caloric intake from fat. Pritikin permits some animal fat, whereas the Ornish diet is vegetarian. Because fat facilitates satiety, diets that severely restrict fat intake may be difficult to follow long-term. Diets that limit fat intake to less than 10% of daily caloric intake may also be deficient in essential fatty acids and fat-soluble vitamins such as A, D, and E; thus, their long-term use should be discouraged.

Dietary practices that maintain total fat intake at 25% to 30% of total calories consumed can be effective for long-term weight control, while providing adequate protein, calcium, fiber, and fluid, all of which are important for older adults. Evidence from the Women’s Health Initiative, a prospective study that included 50,000 women, found no significant difference in weight loss between individuals on a normal diet and those following a low-fat diet.²⁰ One advantage of low-fat plans is that they generally emphasize greater consumption of fruits and vegetables, which are low-calorie, nutrient-dense foods.

Plant-based Diets 
Several population-based studies have shown that individuals following a plant-based diet have a lower body mass index than nonvegetarians, indicating a plant-based diet may be a viable approach to weight management.^21,22 Ample fruits, vegetables, nuts, legumes, grains, and polyunsaturated fats are included in plant-based diets. Plant-based diets can be categorized into three distinct types: vegan, which excludes the consumption of any animal products, including meat, poultry, fish, dairy, and eggs; lacto-vegetarian, which permits dairy products such as milk, cheese, and yogurt; and lacto-ovo vegetarian, which permits both eggs and dairy.

Although there has been some concern that this diet may be lacking in micronutrients such as iron and zinc, studies to date have not provided substantial support for this concern. Recently, Farmer and colleagues²³ reported an assessment of the 1999-2004 National Health and Nutrition Examination Survey data, which showed mean intakes of fiber, thiamin, riboflavin, folate, calcium, magnesium, iron, and vitamins A, C, and E in vegetarians exceeded that of nonvegetarians. In addition, the Healthy Eating Index score, a measure of diet quality established by the US Department of Agriculture, did not differ for vegetarians compared with nonvegetarians. Based on these findings, the authors conclude “vegetarian diets are nutrient dense, consistent with dietary guidelines, and could be recommended for weight management without compromising diet quality.” Another recent study examined the health aspects of nutrition and physical characteristics in matched samples of institutionalized vegetarian and nonvegetarian elders older than 65 years.²⁴ This study showed a similar mean dietary intake between vegetarians and nonvegetarians; comparable blood values of vitamin B₁₂, folic acid, iron, calcium, and zinc, the latter of which was below the reference value in both groups despite estimated zinc intakes being in agreement with the recommended daily intake; and similar physical abilities (eg, handgrip strength results). Based on these findings, the authors conclude “vegetarian lifestyle has no negative impact on health status at older age.”

Most nutrition studies do not report measures of zinc status because there are currently no reliable biochemical markers to assess for this. However, because zinc is found primarily in foods of animal origin, zinc supplementation should be considered in individuals following a plant-based diet.

In addition to showing no harmful effects with a plant-based diet, many studies have shown this diet to confer significant health benefits, including demonstrating its viability in reducing insulin resistance and oxidative stress markers in patients with type 2 diabetes mellitus,²⁵ preventing heart disease,²⁶ managing recurrent prostate cancer,²⁷ and reducing the incidence of diverticular disease.²⁸  As a weight management strategy, a plant-based diet also has several advantages. Plant-based foods are generally nutrient dense. In addition, because fruits and vegetables contain mostly water and are low in calories, a higher volume of these foods can be consumed to achieve a feeling of satiety and allay excess energy consumption.

Portion-control Diets
Portion-control diets, such as Weight Watchers, Jenny Craig, and NutriSystem advertise heavily on television and social media networks, often using celebrity spokespersons. These diets emphasize calorie reduction, group support, and exercise recommendations.³ As with many low-fat diets, portion-control diets typically encourage dieters to eat a wide variety of foods, including lean proteins, whole grains, fruits, and vegetables, making them safe for most people to follow long-term.³ All three aforementioned plans require dieters to subscribe as members and pay membership fees.

Weight Watchers uses a point system to cut calories. Various foods are assigned different point values based on their fat, fiber, protein, and carbohydrate composition. As part of a recent update to its points system, Weight Watchers reduced the point values for most fruits and vegetables to 0, enticing dieters to incorporate more of these nutritious foods into their diet. Weight Watchers has also added activity points to its plan, enabling dieters to earn additional points to their total daily or weekly allotment of points. Members’ daily point allowance is calculated individually based on starting weight and the desired weight loss goal, and is recalculated to promote weight maintenance when the member successfully achieves weight reduction. Dieters can use foods they prepare themselves or purchase Weight Watchers’ branded foods, which are available at most grocery stores. Many other diet foods available at the grocery store conveniently list Weight Watchers’ “point value” and at least one restaurant chain has added Weight Watchers’ point values to its menu. 

Jenny Craig’s plan helps members monitor caloric intake by providing prepackaged foods that are delivered to the home or purchased at a local Jenny Craig facility. As members advance through the program, Jenny Craig representatives design individualized menus using foods that can be prepared at home.

NutriSystem is another popular weight loss program that achieves portion control through the use of prepackaged meals. Both Jenny Craig and Weight Watchers provide group support through regular meetings and an online community (both offer a less expensive online-only option); however, NutriSystem offers online support only. NutriSystem features a variety of meal plans, including vegetarian, diabetic, and low glycemic index foods. It also has a selection of foods with reduced sodium and provides exercise plans.

A significant advantage of the Weight Watchers and Jenny Craig plans is long-term behavioral and lifestyle coaching through group support. Both plans promote exercise as a key component of weight control. The availability of packaged entrees and snacks offers convenience by taking the guesswork out of calculating each food’s points or calories. Prepackaged portion-control diet systems can be costly due to membership fees, supporting materials (eg, books, scales, periodicals), and—at least for Jenny Craig and NutriSystem—the requirement that members purchase prepackaged foods. Consumers should remain mindful of the sodium content of prepackaged foods in addition to the total energy value in light of the association between elevated blood pressure and chronic excess dietary sodium intake.

Supplement-supported Diets 
While elders sometimes require nutritionally complete supplements to help sustain or promote weight gain, the use of weight loss regimens that requires the use of herbal or chemical supplements should be discouraged. Elders generally have comorbidities and take multiple prescription medications. Over-the-counter dietary supplements may have unintended interactions with prescribed medications. They also are not subjected to the strict quality-control measures mandated by the US Food and Drug Administration (FDA) for prescription medications, and they may contain unknown and potentially harmful ingredients, or levels of ingredients out of proportion to that listed on the label. The FDA has issued warnings regarding specific weight loss products. In 2008, it alerted consumers that 69 weight loss products it had tested contained undeclared, active pharmaceutical ingredients, including agents such as sibutramine, an anorexiant; rimonabant, an anorexiant not approved for use in the United States and withdrawn from the European market because of its potential to induce significant psychiatric effects; phenytoin, an antiseizure medication; phenolphthalein, a solution used in chemical experiments and suspected to be carcinogenic; and bumetanide, a diuretic.²⁹ In some cases, the amounts of active pharmaceutical ingredients in the weight loss products far exceeded the FDA’s recommended levels, putting consumers’ health at considerable risk.

Providing an overview of all of the various supplements available, such as fat burners, lipase inhibitors, and appetite suppressants, is well beyond the scope of this paper. However, we briefly review two popular supplements that have been marketed as facilitating calorie restriction. One agent has been on the market for decades, whereas the other is fairly new.

The Human Chorionic Gonadotropin Diet. In 1954, British physician Albert T. Simeons reported that human chorionic gonadotropin (HCG) injections enabled dieters to limit their intake to 500 calories per day, helped mobilize stored fat, suppressed appetites, and redistributed fat from hips, thighs, and waist.³⁰ Simeons injected participants with HCG 125 mIU/mL 6 days per week. He claimed that his subjects lost weight because the hormone suppressed their appetite and improved their mood. The most notable adverse effects of the HCG injections were hypoglycemia, increased libido, elevations in uric acid, and gout.³⁰

In 1973, Asher and Harper³¹ conducted a prospective, randomized, double-blind study comparing the effectiveness of HCG versus placebo at inducing weight loss. Individuals in the HCG group lost significantly more weight and had a significant decrease in hunger compared with those in the placebo group; however, subsequent studies found no weight loss benefit with HCG treatment.^32-35 One study reported significant declines in hematocrit, white blood cell count, blood urea nitrogen, cholesterol, triglycerides, and total protein among participants assigned to HCG, which the authors attributed to nutritional deficits associated with consuming fewer than 500 calories daily.³² A meta-analysis of HCG diet trials concluded that there was no scientific evidence supporting HCG as an effective treatment for obesity; it did not result in redistribution of fat, reduce hunger, or induce a sense of well-being; and HCG should not be promoted as a weight loss method.^36,37 Despite the evidence against HCG’s effectiveness, HCG drops, pellets, and sprays were sold over-the-counter as homeopathic weight loss aids in the United States until December 2011, when the FDA declared these products unproven and illegal.³⁸ Nevertheless, these products can still be purchased through the online market.

The Sprinkle Diet.  The sprinkle diet, also known as “Sensa,” claims that sprinkling tastant crystals (made from maltodextrin, tricalcium phosphate, silica, and flavors) on food enhances its smell, tricking the brain into feeling full sooner and leading to consumption of less food. On the product’s Website, claims are made that a clinical study demonstrated the efficacy of this agent, with those using the tastant crystals losing an average of 30.5 lb after 6 months compared with a weight loss of only 2 lb in the control group.³⁹ However, the validity of this study is questionable, as it was a company-sponsored study and the results have not been published in any peer-reviewed medical journals. More importantly, the fundamental concept of this “diet” is significantly flawed, as it does not support exercise or healthy eating habits and leads people to believe that behavior change is unnecessary to achieve healthy weight loss. Ironically the Website prominently features Sensa being sprinkled on low-calorie foods, such as salads, and no strategy for weight maintenance is promoted by the manufacturer of this product.

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Comparing Popular Diet Plans

Truby and colleagues⁴⁰ recruited a cohort of 300 adults aged 18 to 65 years and compared different classes of diets: Atkins (low-carbohydrate), Weight Watchers (reduced calories and support group), Slim-Fast (liquid meal replacement), and the Rosemary Conley diet (a low-fat diet plan with group exercise based in the United Kingdom). Participants were excluded if they had a diagnosis of diabetes, hypertension, hyperlipidemia, or heart disease. The study found that it was possible to lose weight adhering to any of the diet options.⁴⁰ At 6 months’ follow-up, each group demonstrated reductions in weight, waist circumference, and blood pressure, with no significant difference between groups. After 1 year, all groups demonstrated clinically useful weight loss, with a mean weight loss of approximately 17.6 lb. Those individuals whose diet plan incorporated social support demonstrated increased adherence at 1 year.

In the A to Z (Atkins, Traditional, Ornish, Zone) Weight Loss Study,⁴¹ Gardner and colleagues assessed the comparative effectiveness of each diet. For the traditional plan, they used the Lifestyle, Exercise, Attitudes, Relationships, and Nutrition (LEARN) diet, which is low in fat and high in carbohydrates. Participants included 239 premenopausal women aged 25 to 50 years who were free of diabetes, cancer, heart disease, and uncontrolled hypertension. Participants were randomly assigned a diet plan and instructed to follow written guidelines for the diet and attend 1-hour classes once a week for 8 weeks.

No significant difference was observed in energy intake at baseline or during the study between the different groups. At baseline, energy expenditure was slightly higher for those in the Ornish group. Overall, participants demonstrated a significant increase in mean energy expended (P<.05) at each of the study’s various end points, but the size of the increase did not differ significantly between the groups. Weight change, percentage of body fat, waist to hip ratio, fasting lipid profile, and blood pressure were measured at baseline and again at 2, 6, and 12 months. Mean weight loss over 12 months was 10.3 lb for Atkins, 3.5 lb for Zone, 5.7 lb for LEARN, and 4.8 lb for Ornish. The amount of weight lost was not statistically different among the Zone, LEARN and Ornish groups, but when compared with the Zone group, the Atkins results were significant (P<.05). All groups showed reductions in percentage of body fat, waist to hip ratio, blood pressure, and triglycerides at 12 months. Overall metabolic profiles were more favorable for participants who were assigned to the Atkins plan.

Prudent Weight Loss Guidelines

A prudent 500-calorie energy deficit plan (500 fewer calories consumed than expended daily) can be created by choosing nutrient-dense foods and practicing portion control while engaging in physical activity. Energy consumption should be maintained at 1200 or more calories daily because taking in fewer calories fails to provide the minimum amounts of important micronutrients, including calcium. The only supplement that is recommended in older adults following a reduced calorie diet is a multivitamin and mineral supplement. This recommendation is made because the efficiency of overall nutrient absorption decreases after 50 years of age.

Food choices should include whole grains, fresh fruits, vegetables, low-fat dairy products, dry beans, peas, and lean proteins. Patients should be encouraged to read food labels and to avail themselves of resources and books that provide sound nutritional information. Reputable sources of information on nutrition include local, state, or federal governments and national scientific organizations and foundations (Table 2).

In addition to controlling energy intake by eating nutrient-dense foods, older adults should be encouraged to perform age-appropriate exercise. A study by Marcellini and colleagues,² which included 150 adults aged 50 to 74 years, showed that people who were not obese tended to walk significantly more than those who were obese (83.2±131.6 min/wk vs 42±99.4 min/wk, respectively; P<.05). The same study also showed that nonobese participants spent significantly more time engaged in sporting activities than obese participants (P<.05). Another recent study showed that combining a weight reduction diet with exercise is more effective at preventing frailty and preserving quality of life for obese older adults compared with either modality alone.⁴²

Lifestyle changes are critical to achieve long-term weight control. Important changes include finding ways to increase the level of physical activity, limiting consumption of fast foods and restaurant meals, eliminating high-calorie drinks from one’s diet, and staying motivated. Registered dieticians can assist patients unable to maintain their weight within a healthy range or who need guidance in making healthy choices in creating a personalized weight loss plan.

Conclusion

Clearly, studies and opinions conflict regarding the comparative effectiveness of various popular weight loss plans. Research assessing the Atkins, Zone, Weight Watchers, and Ornish diets suggests all are equally effective at reducing weight when followed for 1 year.³ Although data appears to associate the Atkins diet with greater weight loss and more favorable metabolic effects at 1 year versus the Ornish, Zone, and LEARN diets, LC/HP diets increase the risk of urinary calcium loss and osteoporosis and are typically low in fiber, potassium, calcium, and B vitamins. Thus, an LC/HP diet may not be the best approach to weight control in older adults, who require adequate levels of calcium, B vitamins, protein, fat-soluble vitamins, fluids, and fiber to maintain healthy bones, muscle mass, and digestive health. The general consensus is that energy reduction achieving a negative calorie balance is the key to weight loss. As such, most diets will be effective provided the patient can sustain a modest energy deficit for an extended period. Overweight and obese individuals often regain weight; therefore, it is essential to encourage patients to establish and maintain healthy behaviors (eg, consume nutrient-dense foods and remain physically active) to preserve and ensure optimal health.

Dr. Steinle receives salary support in part from the Mid-Atlantic Nutrition Obesity Research Center (NORC), University of Maryland School of Medicine - NIH Grant P30 DK072488. The other authors report no relevant financial relationships.

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