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Debunked by a Dietitian: Fad Diets, Part Two

The Good and the Bad About Popular Nutrition Plans

This is the second in a two-part series on the facts about fad diets, focusing on long-term trends. To learn about limited time programs like the Whole 30 or juicing, please read part one.

The most effective healthy eating is habit-based. Ongoing efforts to eat a diet based on fruits and vegetables, whole grains, and lean sources of protein will offer your most complete healthy diet. But long-term healthy habits and nutrition trends aren’t mutually exclusive.

If you’re following a diet for health concerns – such as food intolerance – working with a nutritionist can ensure you’re receiving the necessary nutrients.

If, however, you’re interested in pursuing an alternative diet for personal or general health reasons, here’s what Edye Wagner, MBA, RD, LDN, CDE, a nutrition expert at Northwestern Medicine, had to say about the most popular trends.


The Mediterranean diet is focused more on how often and how much you eat rather than what exactly you eat. It’s not a free pass though: the diet is plant-based, predominately fruits, vegetables, whole grains and healthy fats, with limited meats and animal products.

The Good: It promotes health and longevity through a number of benefits: high in antioxidants and anti-inflammatory foods, low in saturated fat and cholesterol, complete in minerals, vitamins and nutrients.
The Bad: The Mediterranean diet requires self-regulation and a pre-existing knowledge of healthy portion sizes. Guidelines don’t often provide exact amounts or specific measurements.
The Verdict: "The Mediterranean diet is considered one of the healthiest ways to eat,” says Wagner.


The phrase vegetarian is often used loosely, to refer not only to plant-only diets, but also those that are plant-based but include dairy, eggs or fish. Generally, these diets can provide all of the necessary vitamins and minerals.

The Good: Plant-based diets are lower in cholesterol and saturated fat.
The Bad: A no-animal-product diet is not inherently healthy. Vegetarians still need to watch sugar and fat intake to make healthy choices.
The Verdict: “Plant-based diets are thought to be better for health. There are many sources of vegetarian recipes that can help people get started on a plant based diet and keep variety in the vegetarian diet,” says Wagner.


Vegan diets are pretty simple: No animal products whatsoever, including no dairy, eggs or fish. That means a diet of predominately vegetables, fruits and grains.

The Good: No animal products means low in cholesterol and saturated fats.
The Bad: Going vegan can require a bit more homework than other diets to ensure you’re receiving all the necessary nutrients. Vegans often need to supplement vitamin B12 in particular.
The Verdict: “Variety is a key to getting all of the minerals and most of the vitamins needed from food,” says Wagner. “And making smart choices and watching portions is always important.”


Short for Paleolithic, the Paleo diet is based on what early humans were thought to have eaten. That means lots of fruits and vegetables as well as meat, fish, eggs, nuts and some oils as well as no dairy, grains, legumes, processed foods or refined sugars.

The Good: Eliminating processed food and refined sugar is always good for you.
The Bad: Many modern grain foods such as whole grain cereals and breads are fortified with vitamins and minerals that are hard to otherwise get in adequate amounts. Paleo also restricts dairy, limiting calcium intake. The diet also does not consider which animal proteins are healthier for us, and how much is too much. Moreover, the Paleo diet can lack variety and be high in saturated fat and cholesterol.
The Verdict: “Today’s lifestyle does not support the Paleo diet’s restriction of healthy nutrients and its lack of restriction of less healthy animal proteins,” says Wagner.


The raw food trend requires food to be uncooked or heated to less than 140 degrees Fahrenheit. It is therefore predominately fruits, vegetables, seeds and nuts.

The Good: No processed foods is a plus.
The Bad: A raw food diet can lack important vitamins and minerals, specifically B12 and D as well as iron and zinc. Food safety can also be a concern: raw foods and unpasteurized dairy can lead to food borne illnesses, which is especially dangerous for a compromised immune system.
The Verdict: Says Wagner, “The extreme restrictions of this diet can lead to nutrient deficiencies and difficulty planning meals.”


A gluten-free diet is a restrictive diet that rose to prominence as a treatment for celiac disease. The gluten protein – found in grains – causes inflammation in the small intestines of people with celiac disease. However, there is no evidence that gluten causes inflammation in the general population.

The Good: If you have celiac disease or have been diagnosed with gluten intolerance, following a gluten-free diet is a very healthy decision.
The Bad: Going gluten-free can be restrictive and expensive. And it’s not necessarily healthier than a traditional diet for most people.
The Verdict: “Choose foods wisely and focus on a plant-based diet rather than restricting gluten if there is no suspected intolerance,” says Wagner.


A lactose-free diet restricts lactose, which is the sugar component in dairy products. As a result, lactose-free eating eliminates or minimizes many dairy products such as milk, cheese and butter.

The Good: Eliminating foods that are high in lactose can help alleviate the gastrointestinal upset that affects many people when eating dairy.
The Bad: Limiting dairy also limits calcium.
The Verdict: Says Wagner, “If a low lactose diet is followed, include foods that are fortified with calcium or discuss daily supplements with your medical team.”

Meal Plans and Delivery

There are a number of healthy eating or diet services that offer meal plans – Weight Watchers and Jenny Craig being two of the best known. These systems often provide approved meals while giving people the tools to apply healthy habits to their future. Often this involves encouraging people to think specifically about what they are eating, particularly if the program involves a point or counting system of some kind.

The Good: Organized plans are generally very balanced and provide structure for people struggling with weight loss or healthy eating on their own.
The Bad: Programs can be expensive and food options may become monotonous over time.
The Verdict: “Meal plans may not be a long term solution to weight loss,” says Wagner. “But they can be a good bridge to healthier eating, and good teaching tools to show examples of proper portions and balanced meals.”