FAT LOSS FOR TYPE 2 DIABETES PREVENTION AND REMISSION

As many people are aware, the available evidence suggests that being overweight or obese accounts for up to 90% of the risk of developing type 2 diabetes. This is of course due to excess body fat – not excess muscle or bone. Therefore, perhaps unsurprisingly, not everyone with type 2 diabetes is overweight or obese as defined by Body Mass Index (BMI). Indeed, at the individual level, BMI is not the best measure of excess body fat (e.g., abdominal fat). Waist circumference; waist : height ratio; bioimpedance analysis; etc…are more useful tools that can be used in clinical practice by suitably qualified health professionals to help determine if you carry excess body fat, in particular around the middle.

While fat (adipose) tissue stores much of the excess energy from foods and beverages, as excess fat accumulates, it is stored in other organs like the liver, pancreas, and muscle. In these non–adipose tissues, excess energy leads to lipotoxicity, meaning that the excess fat stored in these cells inhibits their optimal functioning. This disrupts normal glucose and insulin metabolism. Muscle lipotoxicity inhibits glucose uptake, causing peripheral insulin resistance, requiring greater amounts of insulin for glucose uptake by muscles. This resistance is reduced with exercise as muscle tissues consume energy and become more responsive to insulin. Pancreatic lipotoxicity inhibits beta cell insulin production, reducing the amount of insulin available to overcome the insulin resistance in muscles and other organs. Significant energy restriction removes fat from the pancreas in a matter of days, restoring beta cell insulin production.

Losing weight for pancreatic beta cell resuscitation

Randomised controlled trials indicate that weight loss of 10–15% (8 – 12 kg for an average adult) may lead to normalization of pancreatic function and remission of type 2 diabetes. There are of course many different ways of decreasing body fat, but the fundamental underlying mechanisms are increasing physical activity, decreasing inactivity (sedentarism), and reducing energy (kilojoules/Calories) consumption from foods and beverages.

No particular macronutrient profile or style of dieting offers advantages over others as the best diet is the one a person can adhere to in the long-term (years, not months). Very low energy diets (VLEDs), low energy and reduced energy diets are all effective methods of energy restriction with different advantages and disadvantages. All people with existing diabetes need to discuss their plans for energy restriction with their health care team, with a view to adjusting glucose-lowering medication (if taken).

Very Low Energy Diets (or Very low Calorie Diets)

As the name suggests, VLED’s provide less than 3,350 kJ (800 Calories) a day. They are typically consumed 3 times per day, for breakfast, lunch and dinner as a specially formulated shake (typically milk based, but plant-based options are becoming available). As well as the shakes, people need to consume at least 2 litres of non-caloric fluids (e.g., water, black tea/coffee, “diet”/no-sugar soft drinks, cordials, etc…) each day. Ideally 2 cups of non-starchy vegetables (e.g., most vegetables other than beetroot, parsnip, peas, potatoes, pumpkin, sweet potatoes, sweet corn, and yams) and/or a suitable dietary fibre supplement (e.g., psyllium) should be consumed to reduce constipation. Additionally, people need to consume 1-2 teaspoons of unsaturated oil (e.g. olive oil, Canola oil, etc…) per day to aid gallbladder contraction in order to reduce the risk of gallstone formation. Finally, depending on the VLED they choose, and their starting body weight, many people may also need to take an additional high quality protein supplement to minimise muscle loss.

Note: VLEDs are generally only recommended for people who have a BMI >30 kg/m2, or >27 kg/m2 if they have weight-related complications like type 2 diabetes. They are unsuitable as a sole source of nutrition for children and adolescents, pregnant or lactating women and the elderly (65+ years). People that have gall stones, gout, advanced renal or hepatic disease, or pancreatitis, or have recently had myocardial infarction (heart attack) or unstable angina should discuss the suitability of using a VLED with their medical doctor or other health care professional.

Low energy (kilojoule/Calorie) diets

Provide 4,200 – 6,300 kJ (1,000 – 1,500 Calories) per day and consist of main meals, snacks, desserts, etc…If designed properly, they are nutritionally complete, providing sufficient protein, fat, carbohydrate, dietary fibre, vitamins and minerals for the typical adult. Weight loss of 10-15% of body weight can be achieved using low energy diets, but the time taken to meet the target is longer than that of VLEDs.

Reduced energy diets

Like low energy diets, reduced energy diets are tailor-made to meet the specific needs of the individual. It is generally recommended that people need to consume ~2,000 kJ (500 Calories) less each day to lose 0.5 kg of fat per week, and therefore for most people, achieving the target weight loss of 10-15% of body weight will take longer than with either low energy diets or VLEDs.

In addition to taking into account individual’s cultural and personal food preferences, construction of the low and reduced energy diets should be based on evidence-based diabetes guidelines and when specific advice for people with diabetes is unavailable, dietary guidelines for the general population (which are not designed for people with diabetes per se).

Conclusion

Reduced, low and very low energy diets can be utilised to help people with pre-diabetes prevent the development of type 2 diabetes or to put people with recently diagnosed type 2 diabetes into remission.

Read more:

• Kelly and colleagues. Type 2 Diabetes Remission and Lifestyle Medicine: A Position Statement From the American College of Lifestyle Medicine. Am J Lifestyle Med, 2020.
• Lean and colleagues. Primary care-led weight management for remission of type 2 diabetes (DiRECT): an open-label, cluster-randomised trial. Lancet, 2018.
• Taheri and colleagues. Effect of intensive lifestyle intervention on bodyweight and glycaemia in early type 2 diabetes (DIADEM-I): an open-label, parallel-group, randomised controlled trial. The lancet Diabetes & endocrinology, 2020.
• Churuangsuk and colleagues. Diets for weight management in adults with type 2 diabetes: an umbrella review of published meta-analyses and systematic review of trials of diets for diabetes remission. Diabetologia, 2022.
• Leslie and colleagues. Weight losses with low-energy formula diets in obese patients with and without type 2 diabetes: systematic review and meta-analysis. IntJObes(Lond). 2017.