Why You Might Not Want to Try Dr. Oz's 21-Day Diet to Help You Lose Weight, According to a Nutritionist


A diet with the word "breakthrough" in the title sets up big expectations. As a result, I was a bit skeptical about Dr. Oz's 21-Day Weight Loss Breakthrough Diet. The free plan, available on the TV physician's website, lays out what to eat and what to avoid over a three-week period, in order to "lose weight, reduce bloat, and boost your energy."

Here are my thoughts as a dietitian on the pros and cons of the approach, and what to consider before you jump on the breakthrough bandwagon.

How is the Dr. Oz Diet structured?

The plan calls for oolong tea first thing in the morning, followed by a small breakfast, a mid-morning snack, lunch, a second snack, and dinner. Beverages include another cup of oolong tea and water.

Certain foods are to be consumed in specified amounts daily, including half of an avocado, one serving of whole grains, three servings of plant protein, two tablespoons of olive oil, two servings of fruit, and an ounce of nuts, or one tablespoon of nut butter. Leafy greens and 30 other non-starchy veggies are allowed in unlimited amounts. A graphic on the Dr. Oz website explains the plan's parameters and daily guidelines.

What foods are allowed?

Foods and the amounts to eat for each meal and snack are laid out either specifically or as options. Breakfast is to include healthy fat and fiber, such as avocado toast made with Ezekiel bread. Fruit is the designated mid-morning snack, and the second snack includes fruit combined with nuts or nut butter. Lunch and dinner meals should be comprised of plant protein from options like beans, tofu, tempeh, or seeds, paired with non-starchy veggies and olive oil.

RELATED: This Healthy Diet Plan Will Jumpstart Your Weight-Loss Goals, According to a Nutritionist

Which foods are nixed?

All processed foods, including bagels, muffins, chips, candy, and the like, are off-limits completely, as are sugar and artificial sweeteners. Animal proteins are limited. The plan allows no more than two servings per week of dairy products, including milk, cheese, and yogurt. Up to twice per week, plant protein can be replaced with animal protein, such as eggs, poultry, fish, and meat.

Pros of the diet

Dr. Oz's diet doesn't require counting or tracking calories, or the purchase of any products or supplements. The emphasis on vegetables, plant-based foods, whole foods, and healthful fats is in line with well-established, research-backed nutrition guidelines. The plan also emphasizes aspects of the Mediterranean diet, which has long been considered the gold standard for reducing chronic disease risk and improving longevity. The diet also offers an alternative to the ultra low-carb keto approach that continues to dominate the weight loss space. Some of the free recipes offered by the plan look good, including the bean chili and container salad.

I strongly agree with the diet's exclusion of artificial sweeteners, which in research has been linked to negative impacts on appetite, heart health, and blood pressure, and an increased risk of weight gain. In terms of real sugar, I advocate for limiting its intake, but the diet's requirement to eliminate it completely is unnecessary (read on for why).

RELATED: The 12 Best Weight Loss Tips, According to a Nutritionist

Cons of the diet

Due to the number of rules, I think a cheat sheet would be needed to keep track of how to follow the plan. And based on the info provided on the Dr. Oz website, I have a few unanswered questions.

For example, other than avocado toast (the breakfast example), when and how do you fit in the one serving of whole grains and half avocado? Can you add something like brown rice or quinoa and avocado to lunch or dinner? What is a serving of whole grain, and why only one serving per day? Also, why aren't starchy veggies such as potatoes, yams, and butternut squash allowed as a carb option?

Another con is that it's a one-size-fits-all diet, with no foreseeable way to modify the plan based on individual needs. It's also short on carbohydrates compared to the amount needed for most adult women daily, not including additional needs to support exercise (even though exercise is encouraged while following the plan). In comparison, most of my active female clients require one half to one cup of whole grain or starchy veggies per meal rather than per day, in addition to two servings of fruit and several cups of non-starchy veggies.

Other downsides include no mention of coffee (something I and many of my clients can't live without!), alcohol, restaurant or takeout meals, or how to adjust the plan if you're allergic or sensitive to nuts, soy, or gluten.

The plan may also fall short on protein or widely vary in its daily protein content. For example, if two tablespoons of seeds are chosen as the plant protein option, the serving adds just five grams of protein to the meal, as opposed to 15 grams in one cup of cooked black beans.

There is a FAQ provided on the site, but I did not find a way to ask more questions, contact a dietitian for guidance, or connect with fellow dieters for support and encouragement. And while the approach borrows from the Mediterranean diet, this specific plan hasn't been researched for its effectiveness or health outcomes.

Finally, even the strictest guidelines on added sugar, released by the American Heart Association (AHA), advise limiting the sweetener to no more than six teaspoons worth per day for women and nine for men. In other words, completely eliminating sugar is not necessary for sustainable weight loss and reduced health risks.

Instead, I advise my clients to enjoy treats that contain added sugar within the recommended AHA cap. These can include better-for-you goodies like dark chocolate, black bean brownies, or maple-baked fruit, or an occasional can't-live-without splurge, like a donut or cupcake. The ability to enjoy sensible amounts of sugar, even for 21 days, is the key to stick-with-it-ness for many. A too strict approach often leads to lingering cravings, overeating "allowed" foods without satisfaction, or eventually binge-eating sugary foods.

RELATED: The 5 Best Weight Loss Tips if You're Over 40

Should you try it?

I would not call this plan a breakthrough, and it's not novel in its approach, as Mediterranean and plant-based diets have been consistently recommended for years. It's simply another limited diet that likely leads to weight loss due to its restrictions. While it's set up for 21 days, the diet's FAQ says there is "no specific limit to how long you can stay on this weight-loss plan." In my experience counseling clients throughout the years, this diet would be difficult to follow long-term without modifications.

That said, it can be a solid starting point for how to eat healthfully, if you tweak it to add more variety, strike a healthier macronutrient balance (especially if you're active), and allow for occasional indulgences. If you decide to give Dr. Oz's diet a try, listen to your body, and make adjustments that allow you to feel well physically, emotionally, and socially. Even if the results are slower, they'll be well worth the wellness tradeoff and sustainability.

Cynthia Sass, MPH, RD, is Health's contributing nutrition editor, a New York Times best-selling author, and a private practice performance nutritionist who has consulted for five professional sports teams.

To get more nutrition and diet tips delivered to your inbox, sign up for the Balanced Bites newsletter