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When Your Doctor Suggests Healthier Eating for Weight Loss: Which Diet Plan?

If you have been warned that you have prediabetes or that you are at risk for developing diabetes and heart disease, you can start by making a few small adjustments to improve your diet.

If you're carrying a few extra pounds, and you've been diagnosed with prediabetes or diabetes, chances are good your doctor has had ''the talk'' with you. Yes, that depressing  ''It would help if you lost weight'' conversation.

Mediterranean diet

Or maybe you're at a healthy weight, but your risk for diabetes is inching up—the fasting blood sugar test results aren't good, for instance—or you have just been diagnosed, your doctor may have told you to clean up your diet.

Despite the recommendation to improve your eating, chances are also good that you left the doctor's office with little more information than that. Now you're understandably puzzled about which plan to adopt and how to put it into action.

It's not your doc's fault, really. Less than a third of U.S. medical schools offer the recommended minimum of 25 hours of nutrition education, according to a 2015 study.1

To bridge their knowledge gap, a growing number of doctors attend continuing medical education conferences including nutrition lectures. At a recent Obesity Medicine Association meeting, four registered dietitians talked about the evidence behind three popular diets for health and weight loss that are often recommended to those with prediabetes and diabetes. If your doctor didn't make the meeting, here is useful information on three evidence-based eating plans, including: 2

  • Mediterranean
  • Vegetarian/Flexitarian
  • Low Carb

The dietitians described the plans, along with obstacles to following each one and the benefits.

Mediterranean Diet

Description: While many think of the Mediterranean eating plan as carte blanche to have unlimited olive oil and red wine, that's not exactly it, says Carrie Dennett, RDN, MPH, a registered dietitian in the Menu for Change Program in Seattle's Polyclinic. The plan focuses on:

  • High intake of vegetables, fruits, beans, lentil, whole grains, olive oil and nuts.
  • Moderate consumption of seafood and red wine (with meals)
  • Low intake of red or processed meat and dairy products.

The eating plan emphasizes protein-rich foods, heart-healthy fats and low-glycemic carbs (those that are absorbed more slowly), vitamins and minerals, phytonutrients and fiber.

What the Research Says: The weight loss benefit from eating Mediterranean, Dennett says, may be due to the plant-based foods that offer high fiber and a lower glycemic load (with less dramatic rises in blood sugar) keeping you full longer.

In looking at the research as a whole, the Mediterranean diet is shown to reduce chronic disease risk as well as your weight circumference, and it's well known that a large waist circumference (35 inches or higher for a woman, 40 or higher for a man) increases diabetes risk.2

One of the strongest studies, Dennett says, is the large PREDIMED study, including nearly 7,500 adults at high risk for cardiovascular disease who adopted the diet and were followed for 8 years. Following the diet reduced the risk of getting diabetes by 40%. Those with diabetes have a higher risk of heart disease, and the diet reduced the risk of heart attack, stroke and cardiovascular disease deaths by 30%.3

What about weight loss? "The research shows that the Mediterranean diet is an excellent way to eat for cardiometabolic health and there is some evidence it can help protect against weight gain," Dennett says. "The evidence on actual weight loss on the Mediterranean diet is not strong." However, she adds, it can reduce body fat, especially in the abdominal area, and that's a healthy improvement.

And, in a recent study, experts found that following the diet and restricting refined carb foods (such as cookies, white bread) in the evening did help those who followed it strictly lose weight. 4

Obstacles: Vegetable haters and those with poor cooking skills may have some trouble adopting this plan, Dennett says. You may also need to get used to eating foods not typically on your menu, such as fish.

Upside: Those who follow the plan do enjoy the fat content, Dennett says, as well as the flavor and variety of foods. Some report a sense of well-being.

Vegetarian Diet

Description: Say ''vegetarian,'' and many people think ''regimented,'' "strict," even "tasteless." Anita Bermann, RDN, MS, a dietitian in private practice in Bainbridge Island, Washington, knows that all too well. By definition, a true vegetarian diet omits meat and a vegan diet eliminates dairy. However, she reassures patients:  "There is no need to follow a strict vegetarian diet."  If a strict vegetarian diet is too overwhelming, she talks about a flexitarian plan, which is mainly plant-based but with occasional meat or fish.2

What the Research Says: Switching from a meat-based diet to a more vegetarian pattern helps reduce A1C, Bermann says.  In one study that looked at the results of six published studies, researchers found vegetarian diets reduced A1C by about .4 percent, which was substantial from a statistics point of view. 5

For those who are not diagnosed with diabetes, those who ate vegetarian, including eggs and dairy, were half as likely to develop diabetes as non-vegetarians, according to the large Adventist Health Study 2.6

Obstacles: Meat lovers are bound to miss their steaks. However, Dennett reminds them, it's not all or nothing, but a continuum, and reducing meat is beneficial, too.

Upsides: Weight control. The same Adventist researchers found the lowest body mass index (BMI) in vegans, followed by semi-vegetarians. The non-vegetarians had the highest, at 28.7 (25 and above is overweight). 7

Low-Carb Diets

Description: Everyone seems to have their own definition of low-carb. However, there are three main patterns, says Megan Moore , RD, CD and Laura Eggerichs, RDN, CD, both clinical nutrition specialists at Swedish Medical Center in Seattle.

  • A low-glycemic index diet, a general eating plan based on how foods affect your blood sugar level.
  • Low-carbohydrate plans, which limit total carbs to 50-15- grams daily.
  • Very low-carb plans, defined as less than 50 grams daily

Low-carb diets, which emphasize fat and protein, have less of an effect on blood sugar and insulin than do higher-carb diets, Moore and Eggerichs say. The fat and protein both help you feel fuller.2

What the Research Says: "The science behind low-carb and why it works is not much about diabetes, but more on weight loss," Eggerichs tells Endocrine Web. As carbs decrease and protein increases, that can spell good news on the scale. Research has found that eating 1.5 g of protein per kilogram of body weight can produce weight loss, she says.8

To translate: A 150-pound person (68 kg) would eat about 102 g of protein daily if their goal was weight loss. Three ounces of salmon has 19 g of protein; 3 oz. of tuna has 23.

Obstacles: Carbohydrate cravers, such as those who love several pieces of toast at breakfast, may have some difficulty. However, there are easy swaps. Instead of a cup of spaghetti, a cup of spaghetti squash (saves 38 g of carbs). Instead of regular bread, try low-carb bread (save 10 or 15 carbs).

Upsides:  "Often, when we work with patients who have diabetes and we put them on a low-carb diet, they are using less insulin, less metformin," Eggerichs says. "And that can affect their weight. With not as much insulin, there is not as much weight gain." 2

Doctor "Exceptions" Weigh In

Two doctors attending the Obesity Medicine Association's Spring Summit meeting, both versed in nutrition, weighed in with EndocrineWeb about their approaches to helping patients lose weight, reduce diabetes risk or improve blood sugar control.

Carl Knopke, MD: The three common diets discussed all have good qualities, says Dr. Knopke, a family medicine doctor who is also board-certified in obesity medicine. He is medical director of Inland Empire Weight Loss and assistant professor of family medicine at UC Riverside. The trick? Helping patients stick with them.

To boost the chance of adherence, he asks patients about their mindsets. For instance, if a patient favors vegetarian, he asks why. "If they tell me ethical [reasons], I will try to push them in that direction," he says, reasoning they would be passionate about the plan.

In his experience, ''low-carb seems to help blood glucose the most, but you can do low carb with all these diets."

Angela Fitch, MD: Before suggesting one diet plan is better than another, it's important to look at the patient's status as far as blood sugar control, plus their medical history, says Dr. Fitch, associate professor of internal medicine, University of Cincinnati and medical director of the UC Health Weight Loss Center.

For instance, she would recommend vegetarian diets for those who have had a history of cancer, based on research that suggests less overall cancer risk in those who follow the plan. Researchers from the Adventist Health Study also reported a decreased incidence of colorectal cancer in vegetarians, especially those who also ate fish.9

For someone with blood glucose levels out of control, she would be likely to recommend low-carb, Dr. Fitch says.