A panel of experts from four countries held a presentation at the 2020 American Diabetes Association (ADA) virtual Scientific Sessions about the latest research on best diets for diabetes and weight loss. The panel looked at very-low-calorie, low-carbohydrate, and Mediterranean diets, along with time-restricted eating. They concluded that all these approaches can work, and each has both advantages and disadvantages.
Diets for weight loss
Several speakers talked more about weight loss than glucose control. John Wilding, DM, FRCP, from the University of Liverpool, UK, spoke about the pluses and minuses of low-calorie, energy-restricted diets (LCDs). He said they are effective for short term-weight loss but hard to maintain.
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“Anyone who is trying to lose weight is facing an uphill challenge,” Wilding said. “I think we have to remember that we’re trying to beat physiology when we’re supporting someone with obesity and diabetes who is trying to lose weight.” But he believes that mild calorie restriction (like 500 calories a day less than usual) can produce mild weight loss and improve glucose control as long as people stay on it.
The advantages of such a diet, according to Wilding, is that people can eat their usual foods and don’t need to buy expensive food replacements or supplements. They don’t have to change their cooking habits; they just have to eat less.
He said more radical very-low-calorie diets (VLCDs) have worked in studies. “For some people, the total diet replacement approach using meal replacements can be useful because it can result in greater initial weight loss, which patients seem to like, and can even result in remission of type 2 diabetes for some,” Wilding said. “But it’s very important to support the transition back to normal food and a healthier diet in the long-term. I think that’s probably the biggest challenge of delivering that approach.”
In addition to being hard to maintain, low-calorie diets have other downsides. According to Marc Joffe, BSPharm, PhD, of the website Diabetes in Control, “Weight loss with calorie restriction lowers the resting metabolic rate and causes losses of lean tissue, leading to declining physical function in aging adults.” Talk with a health professional about these issues before trying a low-calorie approach.
Low-carbohydrate diets for diabetes
Australian dietitian Jessica Turton, APD, BAppSc (Ex&SpSc), MNutrDiet, spoke about the importance of limiting carbohydrate intake. “We’ve known for a long time that diabetes is a disease of carbohydrate metabolism,” she said, “so [correcting] an excess of carbohydrate intake is likely to be patients’ primary nutritional priority.” Carbohydrates are sugars and starches, which can come from foods like grains or from starchy fruits and vegetables.
Turton advised that low-carb isn’t a whole separate diet from other approaches. It can be combined with them, working with a medical nutritionist.
Studies reported in “Low Carbohydrate Diets the Future for Weight Loss in Obesity” on Diabetes in Control found low-carbohydrate diets as effective as low-calorie diets for weight loss, “while preventing the loss of skeletal tissues. Previous studies have reported that low-carb diets resulted in much lower insulin resistance and improved insulin sensitivity.”
There are many low-carb diets available online, but Turton advised consulting with a health professional to find the best version for you. She said patients want to be sure of getting all the micronutrients (like vitamins) they need on a low-carb diet.
The Mediterranean diet for diabetes
Miguel A. Martinez-Gonzalez, MD, PhD, Professor at the University of Navarra in Spain, discussed the Mediterranean diet. “The Mediterranean diet has a long history of use without any evidence of harm,” he said. Martinez was lead investigator in the PREDIMED trial of 7,447 participants, approximately half of them with type 2 diabetes and the other half with three or more major cardiovascular risk factors.
Patients were randomized to an American Heart Association low-fat diet or a Mediterranean diet. The Mediterranean diet group, both with and without diabetes, “had a reduction of 30% in the occurrence of cardiac clinical events,” Martinez said. “And while weight loss with the Mediterranean diet may not be as great as other diets, studies show that compliance is high and people maintain that weight loss better.”
Mediterranean eating plans are typically high in olive oil, fish, fruits, vegetables, nuts, seeds, beans and lentils, whole grains and garlic. They are low in red meats, dairy and desserts.
This might be lot of changes for people with a standard American diet. One issue is that some of these foods, like olive oil and nuts, can be expensive. Olive oil is less costly in large quantities such as can be purchased at stores like Costco or Walmart. Cheaper but possibly less-healthy products blend olive oil with another oil, usually sunflower oil. Almost-as-good alternatives include grapeseed oil and peanut oil, according to some nutrition websites, but these oils have not been studied as much as olive oil.
Dietitian and diabetes educator Alison Massey, MS, RD, LDN, CDCES, gives additional tips for switching to the Mediterranean style of eating in this video.
Managing diabetes by changing when you eat continues to show good results in small studies. Thomas Pieber, MD, Professor of Medicine at the University of Graz, Austria, said that time-restricted feeding is generally defined by limitations in food intake, with four to 12 hours between meals. With this approach, a person might eat only twice a day, or might have no food between, say, 6 PM and 6 AM.
Another time-restricted form of eating is called intermittent fasting, which usually involves 24 hours or more of no caloric intake, or a very low amount, followed by a return to regular eating for 24 hours. “All of these interventions have shown body-weight reduction and improved glycemic control and cardiovascular risk profile,” he said.
Pieber warned that we have few studies documenting long-term effects of these approaches, and almost nothing comparing the different eating patterns. If you want to try this, you will have to do your own research and consult with a dietitian or nutritionist.
Mix and match
The ADA Meeting News summed up the panel like this: “While experts may not agree which diet is best for the treatment of diabetes and obesity, most agree that there’s no one-size-fits-all diet. The optimal approach often involves a combination of lifestyle modifications, including diet, and medical therapies.”