At any given time, over 100 million Americans are on a diet (MarketResearch .com 2014). That’s about a third of the U.S. population. Despite the hundreds of best-seller diet books and the $60-plus billion Americans spend trying to lose weight each year (Marketdata Enterprises 2014), permanent weight loss remains elusive for most. Even so, dozens of diets remain on the market, each with ardent followers and outspoken opponents.
With so many options to choose from and such avid attempts to “get it right this time,” clients may consult you for advice or directly ask what you think about a particular diet. How do you inform yourself, support your clients’ efforts and stay within scope of practice? This article reviews the pros and cons of the most popular diets, looks at pertinent research, and offers tips on how to approach this sometimes complex topic.
Weight loss diets usually share at least two key features: They cut calories, and they recommend some “ideal” proportion of intake from the macronutrients (carbohydrates, protein and fat). Most diets fall into one of three categories, based on macronutrient composition: low carbohydrate, low fat and moderate macronutrient (balanced). Within each category, the diet “rules” vary considerably. Some heavily restrict certain foods, while others focus on a particular macronutrient. Others allow everything “in moderation,” while still others require specific prepackaged foods. Some— such as the DASH (Dietary Approaches to Stop Hypertension), Mediterranean, gluten-free, vegetarian and Paleo diets—are better described as “eating plans,” since they do not advocate any specific caloric restriction, but rather focus on other parameters. Like “diets,” these plans can contribute to weight loss if clients eat fewer calories overall. An overview of 20 of the most popular diets is highlighted in the sidebar “A Breakdown of Popular Diets.”
What the Evidence Says About a “Best” Diet
Advocates of various diets tend to have a physiological or nutritional explanation as to why their diet is superior. High protein intake may improve feelings of fullness and thus decrease caloric intake and enhance weight loss; low fat intake, says strong evidence, reduces the risk of a life-threatening cardiovascular event. Several studies have looked at these diets, and variations of them, in head-to-head studies comparing weight loss as well as health markers.
Two rigorous and comprehensive diet studies were published last fall. One, a meta-analysis of randomized controlled trials (RCTs) in the Journal of the American Medical Association (Johnstone et al. 2014), looked closely at weight loss. Another was a sys-tematic review of RCTs, published in Circulation: Cardiovascular Quality and Outcomes; it assessed weight loss and cardiovascular risk factors (Atallah et al. 2014).
The meta-analysis (Johnstone et al. 2014) compiled all of the RCTs to date on diets for overweight or obese individuals. The researchers then looked at weight loss 6 months and 12 months after starting the diet. On the whole, at 6 months Atkins dieters had lost the most—an average of 22 pounds. But by 12 months, weight loss across all of the diets was similar. A low-carbohydrate diet and a low-fat diet led to 13 and 15 pounds of weight loss, respectively. This was about a 7% loss of total body weight (it is well established that a 5%–10% weight loss promotes health benefits in individuals who are overweight or obese [NIH 1998]). The moderate macronutrient composition diets—for example, LEARN (Lifestyle, Exercise, Attitudes, Relationships, Nutrition), Weight Watchers and Biggest Loser— led to about 8 pounds of weight loss. Considering that these diets are generally easier to adhere to, they could prove to be more effective eating plans for the long run. However, data beyond 1 year are not available, and the authors were unable to assess the degree of adherence to each of the plans.
The systematic review (Atallah et al. 2014) looked specifically at the weight loss and cardiovascular risk factor effects of four diets (Atkins, South Beach, Weight Watchers and Zone), based on a review of 12 RCTs. Some of these trials compared individual diets with usual care, while others compared the diets with one another. The researchers found that all diets led to some loss of weight, which was at least partially regained 1 year later. Weight Watchers was noted as the only diet that consistently led to weight loss that was at least partially sustained across all studies. Even then, the weight loss was moderate (8–10 pounds at 1 year), much of the weight was regained, and the results did not differ significantly from those of other diets when evaluated head-to-head. The diets that were reviewed appear to contribute to moderate improvements in blood pressure and cholesterol and minimal improvements to blood sugar measures. The number of quality studies assessing these measures is limited.
These findings are in alignment with each other and with most other high-quality diet studies, but not entirely. In fact, in the weeks preceding publication of the meta-analysis and the systematic review, a highly publicized RCT was published comparing a low-carbohydrate diet with a low-fat diet (Bazzano et al. 2014). This study found that a low-carbohydrate diet contributed to increased weight loss and an improved health profile at 3, 6, 9 and 12 months. A comparison of the meta-analysis (Johnstone et al. 2014) with the results of the new low-carb versus low-fat diet study shows that the amount of weight loss at 1 year was about the same for the low-carbohydrate diet (about 15 pounds at 1 year); however, in the new study, the amount of weight loss for the low-fat diet was lower (just 2–3 pounds). This study was fairly small—just 148 participants. It is unclear why weight loss on the low-fat diet was so much less in this study than in other RCTs.
The main takeaway from these studies is that it isn’t so much about which eating plan people follow to lose weight, but rather about whether they can cre- ate enough of a caloric deficit to lose weight and keep it off. While the “best- diet debate” may continue indefinitely, the preponderance of scientific evidence supports a clear conclusion: When it comes to weight loss, it doesn’t matter which diet a person follows, as long as he or she can stick with it. The weight loss is likely to be modest, and once adherence falters, much of the weight lost is likely to be regained. For information about how to coach clients on eating plans while staying within scope of practice, read the sidebar “Answering the Age- Old Question ‘So, What Do You Think About This Diet?’”
Of course, weight loss is not the only factor that clients should consider when preparing to make significant nutrition changes. The quality of food intake may go a long way toward optimizing overall health and quality of life. Independent of weight loss, high-quality eating plans such as DASH and Mediterranean enjoy a large body of evidence supporting their effectiveness in improving health parameters like blood pressure, cholesterol, blood sugar, cognitive function and other factors (Eckel et al. 2013; Rees et al. 2013; Wengreen et al. 2013).
For best results, a client who is over-weight or obese will consider a lifestyle change that incorporates 5%–10% weight loss and a health-promoting eating and exercise plan.
Each year U.S. News & World Report takes into consideration scientific evidence and expert feedback to rank 32
of the most popular diets. They are ranked according to these criteria: best diets overall, best commercial diets, best weight loss diets, best diabetes diets, best heart-healthy diets, best diets for healthy eating, easiest diets to follow and best plant-based diets (U.S. News 2014). Clients looking to start a diet may find this a useful resource in weighing the pros and cons and choosing a plan that best meets their needs. Rankings are available at http://health .usnews.com/best-diet.
A Two-Step Approach to Working With Clients
Fitness professionals commonly work with clients who are contemplating or already following various eating plans. When you are working with one of these clients, a useful approach is to listen carefully to the client’s reasons for following a particular eating plan; any positive and negative experiences with the plan to date; and what he or she says about adherence and commitment to the eating plan. The process of listening and withholding advice will help build rapport and strengthen your relationship with the client. As a general rule, offer advice or information only if specifically asked, or with permission.
Also carefully consider if there is any reason the client’s eating plan sounds unsafe or dangerous. If so, be more assertive. Refer the client to a registered dietitian or personal physician
Take the Quiz
www.ideafit.com/ifjquiz or mail the quiz on page 90. for further investigation and recommendations. If there is no reason to be concerned, support the client in his or her nutritional choice and be available to help optimize adherence.
From Diet to Lifestyle
Clients follow dietary practices for many reasons, most often because they believe that an eating plan will be particularly effective at helping them lose weight. In most cases, with proper planning, any of a variety of different types of eating patterns can be healthful and can contribute to weight loss, especially if the client is able to sustain the eating plan. Thus, a meaningful intervention is to help the client transform the diet into a lifestyle change by supporting adherence both to the eating plan and to a physical activity regimen, which is a well-established requirement for weight loss maintenance.
Atallah, R., et al. 2014. Long-term effects of 4 popular diets on weight loss and cardiovascular risk factors: A systematic review of randomized controlled trials. Circulation: Cardiovascular Quality and Outcomes. http://circoutcomes.ahajournals.org/content/early/2014/11/CIRCOUTCOMES.113.000723.
Bazzano, L.A., et al. 2014. Effects of low-carbohydrate and low-fat diets. Annals of Internal Medicine, 161 (5), 309-18.
Coughlin, J.W., et al. 2013. Behavioral mediators of treatment effects in the Weight Loss Maintenance Trial. Annals of Behavioral Medicine, 46 (3), 369-81.
Donnelly, J.E., et al. 2009. American College of Sports Medicine position stand. Appropriate physical activity intervention strategies for weight loss and prevention of weight regain for adults. Medicine & Science in Sports & Exercise, 41 (2), 459-71.
Eckel, R.H., et al. 2013. AHA/ACC Guideline on lifestyle management to reduce cardiovascular risk: A report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines. Circulation. doi: 10.1161/01.cir.0000437740.48606.d1/-/DC1.
Johnstone, B.C., et al. 2014. Comparison of weight loss among named diet programs in overweight and obese adults. Journal of the American Medical Association, 312 (9), 923-33.
Marketdata Enterprises. 2014. The U.S. Weight Loss & Diet Control Market (12th ed.). Lynbrook, NY: Marketdata Enterprises.
MarketResearch.com. 2014. Weight management: U.S. consumer mindsets. Accessed Jan. 6, 2015. http://helath.usnews.com/best-diet.
Wengreen, H., et al. 2013. Prospective study of dietary approaches to stop hypertension–and Mediterranean-style dietary patterns and age-related cognitive change: The Cache County Study on Memory, Health, and Aging. American Journal of Clinical Nutrition, 98 (5), 1263-71.
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