Author: Dr Roxanne Becker

Introduction
Though it may seem like just a first-world problem, type 2 diabetes (T2D) is a huge burden in the South African healthcare system. According to South African data published in 2022, of over 6000 individuals screened, 67% were prediabetic. (1) While this isn’t necessarily a representation of the entire population, anyone who works in South African hospitals can confirm that regardless of whether you work in an obstetric, medical, surgical, or other ward, you are sure to encounter T2D on nearly a daily basis. Obesity is one of the main risk factors for T2D, and according to research done by the University of the Witwatersrand, 50% of South Africans are either overweight or obese. (2)

Is Type 2 Diabetes Reversible?
It has been estimated that as many as 70% of cases of T2D are due to a suboptimal diet, reiterating that T2D is a disease of lifestyle. Remission is a more appropriate word to use in this context because after achieving remission, T2D can easily recur if old habits are readopted. (3) The good news is that if diet is the largest contributor to T2D incidence, then diet could also be the key to T2D remission. In 2020, the American College of  Lifestyle Medicine released a position statement in which they concluded, “Remission should be the clinical goal in T2D treatment, using properly dosed intensive lifestyle”. (4) With remission possible, all healthcare professionals should be aware of dietary interventions that can assist their patients.

The underlying pathophysiology
Diets high in excess calories and saturated fat (found in animal products, processed foods and tropical oils) have been shown to induce insulin resistance due to the accumulation of lipid in the cells. Intramyocellular and intrahepatocellular lipid (in the muscle and liver cells) disrupt the cascade of reactions that occur in the cell when insulin binds to its receptor, meaning that glucose ports do not function and glucose cannot enter the cells. (5) Plant-based diets have been shown to reverse this accumulation of lipid inside the cells. A randomized control trial placed 244 individuals on a low-fat, vegan diet or a control diet. After 16 weeks, hepatocellular lipid content decreased in the intervention group by 34.4%, and myocellular lipid content decreased in the intervention group by 10.4%. (6)

However, it’s not just the long-term accumulation of intracellular fat that leads to insulin resistance, but just a single meal can impair insulin sensitivity. In a metabolic ward trial, individuals were given a high-fat meal (containing 60g of fat) and a low-fat meal (containing 10g of fat) which were otherwise matched for carbohydrates and glycemic load, and their glucose and insulin requirements were recorded. After consuming a high-fat meal, their initial peak in their blood glucose was higher and remained elevated for longer, and they also required more insulin. (7)

Plant-based diet
An interventional trial done in India, published in 2023, placed 2764 individuals with T2D on a vegan diet and gave them an exercise program and stress management support. After one year, 837 (30.3%) patients achieved remission. (8) Remission was highest in those who never started medication (79%) followed by those only on oral hypoglycemic agents (31.7%). Another case series, also published in 2023, found that after 6 months on a low-fat, plant-predominant diet, 37% of individuals were able to achieve remission. (9)

A subset of the CORDIOPREV study looked at 177 individuals newly diagnosed with T2D, who had not yet started diabetic medication, and randomized them to either consume a Mediterranean-style diet or a diet comprising less than 30% of daily calories from fat. After 5 years, they found that when participants increased their intake of plant protein (accompanied by reducing total and saturated fat intake, and increasing carbohydrate, vegetable, whole grain, nut, and legume intake) they had a 71% higher chance of achieving remission. (10)

The Mediterranean diet places an emphasis on unrefined plant foods, while including olive oil, low-fat dairy and fish. In the Reverse Diabetes 2 Now trial, after 24 months on a Mediterranean diet, 28% of participants ceased all glucose-lowering medication, and 71% of participants using insulin at baseline were off insulin therapy. (11)

Improvements in insulin sensitivity can occur within just a few days. In a randomized crossover trial, within a week of making dietary changes, insulin requirements dropped and insulin sensitivity improved. This crossover trial compared a DASH diet (Dietary Approach to Stop Hypertension diet – includes dairy, eggs and lean meat) with a whole food, plant-based diet (does not include any oils, processed food or animal products, and maintains a fat intake of 10% of total calories), and it found that when participants ate the plant-based diet, their insulin requirements fell even further, and they had greater improvements in insulin sensitivity, suggesting that even lean meat and dairy contribute to insulin resistance. (12)

Other dietary approaches
A very low-calorie diet, comprising meal replacement shakes followed by an isocaloric, low-calorie diet of food, has also been shown to induce T2D remission. (13,14,15) However, remission is largely determined by weight loss, and when the weight is regained, T2D returns. The main concerns with very low-calorie diets is the long-term sustainability of consuming so few calories, as well as potential nutrient deficiencies due to insufficient calorie consumption.

A ketogenic diet has also been shown to improve HbA1c and glucose, due to participants consuming very low amounts of carbohydrates. (16) However, a ketogenic diet, due to its high saturated fat content, does not address the underlying intracellular lipid accumulation and the cause of insulin resistance, and so when individuals who follow a ketogenic diet consume carbohydrates, their blood glucose will be dramatically elevated, again questioning the sustainability of this diet. The ketogenic diet also promotes a high consumption of meat, which has been shown to increase the risk of various cancers such as colorectal (17) and breast cancer, (18) cardiovascular disease, (19) hypertension, (20) and dyslipidemia. (21) While ketogenic diets may promote weight loss and short-term improvements in glycemic control, the long-term risks appear to outweigh the short-term benefits.

Conclusion
T2D is no longer the incurable disease we once believed. It is a disease that can be placed into remission through a predominantly plant-based diet, and other lifestyle factors such as a regular exercise program and quality sleep may increase the chance of remission. Remission should be the clinical goal when treating T2D, rather than only preventing diabetic complications.

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