Published by the Students of Johns Hopkins since 1896
April 16, 2024

Nutrition explained: digesting fad diets

By KELLEN MCGEE | February 28, 2013

For New Year’s resolution-ists, new eating and exercise plans have either proven their worth or fizzled out by now. The desperate search for the perfect path to health continues for many, be they a competitive athlete reaching for a personal record, or just someone looking to cut back on their daily frappuccinos from Starbucks.

Unfortunately, magazine and book publishers, authors, health clubs, food marketing agencies, and personal trainers have figured out how to turn the public’s hyper-focus on health into a pretty penny. As a result, supermarket stocks of high-priced “health food” items have multiplied, virtually every magazine in the checkout aisles makes some claim about weight-loss magic and bookstores give best-selling diet books a special table all to themselves.

The definitions of popular diets are easily digestible: vegetarians avoid meat, vegans avoid all animal products —including eggs, milk, cheese and even honey for the hard-core—, raw-ists can’t eat anything that has been heated above about 115 degrees Fahrenheit, and people following the Paleolithic diet avoid anything that presumably wasn’t available to members of a hunter-gatherer society.

Inundated with all of these different options, what’s a health-conscious but critically-minded Hopkins student to do? Credible, data-driven information about any of these highly-advertised diets is usually difficult to find; even for those who do have access to academic research in health and nutrition, the science can be difficult to interpret. Ann McDermott, an associate professor of human nutrition at the Bloomberg School of Public Health, encounters this issue on a daily basis.

“Scientific studies are controlled for many variables and are taken down to a very artificial scenario,” McDermott said. “They are looking at just one component of [the diet].”

Since each study is conducted on a very specific time scale, it is difficult to compare results across the board. McDermott emphasized the importance of considering the difference between results produced in a study’s brief time-window versus the lifetime period.

Some researchers go back to participants after the study and ask whether they were able to keep off the weight as a way to measure the effect of a diet. In many cases, looking at the long-term effects, including sustainability, dramatically change how different diets compare to each other.

The vast claims made by heath advertisers are not always effective measurements because real-life isn’t that highly controlled, and can’t be counted on to reproduce the results of studies. For example, studies strictly control daily activity to try and isolate the effects of dietary changes, but in real life, McDermott said one good behavior can often lead to another. Someone altering their diet for health reasons, for example, is also more likely to begin exercising, which obscures benefits of the diet alone.

Self-monitored studies have similar errors to consider since people of varying BMI indices tend to report their calorie-intake differently. According to McDermott, people with a higher BMI tend to under-report their caloric intake, and vice-versa.

Given this confusing wash of information, anecdotal evidence has become very powerful in informing the public about diets. Scott Jurek may not be a household name, but he’s one of the rulers of the ultra-running world. He won the Spartathalon, a 153mi-race between Athens and Sparta in Greece, three consecutive times with a personal best of 22:20:01 in 2008, and also holds the US record for distance covered in 24 hours — a whopping 165.7 miles. So, with a record like that, people naturally sit up and listen when he talks about nutrition.

In his new book, Eat Vegan & Run, Jurek credits his success to his vegan, or, as he prefers to call it, “plant-based” diet. He acknowledges that some feel the vegan diet, which avoids all animal products, is too restrictive. However, Jurek has reported the diet’s innumerable benefits since becoming a dedicated vegan in 1999, including lowered blood pressure and triglyceride levels, all-time high “good” cholesterol, decreased soreness and increased energy.

Despite the potential health benefits, McDermott called veganism “an extreme dietary pattern,” and cautioned against blindly following a restrictive diet without proper supplements. For example, since vitamin B-12 is only found in animal muscle, vegans risk becoming deficient if they do not supplement their diet somehow. This deficiency can lead to symptoms imitating Alzheimer’s disease.

“Anything you do extreme, you really need to understand what you are doing biochemically. You must be really knowledgeable about how to get micronutrients from other sources,” McDermott said.

The sources for health and diet information clearly vary, but professionals have their own preferences. McDermott highly recommends the website maintained by The American Dietary Association, the world’s largest organization of food and nutrition professionals ( At this free-to-access site, consumer diet and lifestyle books are independently reviewed and compared to each other.

Even this amount of information can be a little overwhelming though. For a quick and easy eating guide, McDermott recommended Dietary Approaches to Stop Hypertension (DASH), developed by a team at the Bloomberg School of Public Health led by Lawrence Appel.

With the intention of reducing hypertension through dietary changes, Appel and his colleagues constructed a dietary plan rich in fruits, vegetables and whole grains, but also included meat and dairy products.  Over an 11-week trial, using non-specialty foods without fat-substitutes, they found that blood pressure was favorably altered in addition to many other suggestive health benefits. Their results have been published in the New England Journal of Medicine, and have since gained national fame with an endorsement from the National Institute of Health.

The DASH plan, which contains sample meal-plans and resources, is available online for free from the National Heart, Lung and Blood Institute. Athletes and inactive individuals alike can follow DASH, regardless of daily caloric needs, since the plan isn’t built around a calorie-restriction.

Ultimately, it seems that the quality of nutrition information is not proportional to what you pay for it. There are many options and resources supported by critical research for people seeking to observe healthier diets and behaviors.

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