If losing weight were easy, there wouldn’t be 10 million different diets out there promising you the moon. But it isn’t easy, and that’s why there are countless methods being marketed as the newest, best, fastest and simplest way to slim down. In truth, any diet that makes bold claims should be taken with a grain of salt – but not too much salt.
With that in mind, one of the diets that makes such claims is the 21-Day Weight Loss Breakthrough Diet pitched by celebrity physician Dr. Mehmet Oz, known as Dr. Oz.
How It Works
This eating plan includes many well-founded nutritional ideas, and many others that are, at best, unproven and hard to follow.
It recommends a mostly plant-based diet, with the following do’s and don’ts.
- Nonstarchy vegetables, like asparagus or broccoli.
- Plant-based proteins.
- Healthy fats.
- Limited amounts of fruit, nuts, nut butters and whole grains.
- Oolong tea.
- Any processed foods.
- Any sugar and artificial sweeteners.
- More than two servings each of animal protein and dairy per week.
You are directed to eat three meals and two snacks every day, drink plenty of water and consume two daily cups of oolong tea. The diet also spells out exactly which foods you can and can’t eat in each group. For example, there are 42 vegetables on his list, including turnips but not carrots or potatoes.
Proteins come from beans, legumes, soy products (like tofu and tempeh) and nuts and seeds (like pumpkin, flax and chia). Some animal protein is allowed, but not much – just two servings a week of meat, fish or eggs.
Healthy fats include fat from avocado – he suggests having half an avocado at breakfast – and olive oil, but no more than 2 tablespoons a day.
Dr. Oz’s diet is not fond of fruit, limiting it to just two servings a day, or whole grains, with just one serving a day.
And then there’s the wild card here: oolong tea. Dr. Oz claims that two cups of this particular tea every day “has been proven to boost your metabolism – which encourages weight loss, lowers cholesterol, aids in digestion and can help stabilize blood sugar. It also increases mental alertness.”
What the Experts Think: Pros
Celebrity-pitched diets should always come with the warning caveat emptor: buyer beware. This one is no different.
Indeed, Dr. Oz has a long history of promoting dubious nutritional advice. A 2014 study in The BMJ analyzed the claims made on 40 randomly selected episodes of “The Dr. Oz Show,” and found that scientific evidence supported just 46% of his claims, contradicted 15% of others and was not found for the remaining 39%. Overall, believable or somewhat believable evidence supported only 1 in 3 recommendations made on his show.
That’s not to say some of the advice in this plan isn’t sound – it is. “The diet is basically a well-balanced, mostly plant-based diet. It eliminates processed foods, sugar and artificial sweeteners and limits animal protein and dairy to two servings of each per week. Eating this way should lead to weight loss,” says Abby Greenspun, a registered dietitian in Westport, Connecticut. “This type of eating is great for weight management, lowering blood pressure, lowering blood sugar, improving gastrointestinal health and reducing inflammation and joint pain.”
Melissa Majumdar, a registered dietitian certified specialist in obesity and weight management, agrees that any eating plan high in vegetables, healthy fats and plant-based protein is healthful. “All of these foods are foods that most of us do not eat enough of and have strong evidence to support eating more of. They are packed with fiber, vitamins, minerals and antioxidants,” she says. Research has found that replacing animal proteins, especially red and processed meats like bacon, sausage, hot dogs and salami, with plant-based proteins can reduce health problems like diabetes, cancer, heart disease and premature death.
And some types of tea may indeed help promote weight loss. A 2018 meta-analysis in the journal Molecules concludes that certain chemicals in green, oolong, black and dark teas “all exhibit measurable weight-loss properties in a large majority of studies.” How they do so is unclear, but may be related to how they affect the gut microbiome and carbohydrate digestion.
What the Experts Think: Cons
On the other hand, “There is no evidence to support that any specific diet works better than others for weight loss,” says Majumdar, the bariatric coordinator at Emory University Hospital Midtown in Atlanta and a spokesperson for the Academy of Nutrition and Dietetics. “In other words, there is not a specific macronutrient profile or specific amount of carbohydrates, protein or fat that has shown better weight loss than other diets.”
In addition, the plan is not tailored to an individual’s specific dietary needs. Perhaps most important, both dietitians warn against any eating plan that restricts options too severely. “As soon as we are told to ‘eliminate’ something, we want more of it,” Majumdar says.
Finally, short-term fixes never set you up for long-term success. “What you do on day 22 and going forward is most important,” Greenspun says. “If this plan causes you to rethink your habits and continue to eat less processed foods and eat more fiber from whole grains, nuts, fruits and vegetables, then that’s great. If you go back to your old habits, then 21 days of healthy eating is basically worthless.”
The Bottom Line
Neither dietitian would support this plan. “I would not recommend any plan that has a time limit and this kind of rigidity,” Greenspun states.
“This diet may work for 21 days, but I would never suggest a change for someone that would be so life-altering for them that they could not sustain it longer than 21 days,” Majumdar agrees.
Instead, both suggest consulting with a registered dietitian nutritionist who can work with you to identify ways to include more of these healthful foods without drastically cutting out entire food groups. “The plan should include foods that the person enjoys eating and shouldn’t cut out their favorite foods or eliminate whole food groups. It should be realistic and meet their health goals, not focus entirely on the scale,” Majumdar concludes.