Diabetes and weight loss - which dietary approach works?

Being overweight makes diabetes control difficult because it can lead to insulin resistance, making it hard for your body to use insulin properly. If you have Type 2 diabetes, losing excess weight can be the most effective way of managing your condition. Apart from the feel-good factor, there’s lots of research to show that losing excess weight improves blood glucose, blood pressure and blood fats (cholesterol) levels and has long term health benefits.

There are many different dietary approaches to losing weight – but there’s no one-size-fits-all approach. Evidence shows that the best approach is the one that YOU are likely to stick to, so for a successful long-term weight loss, small and realistic changes are crucial. The clue is to find a plan that you enjoy and fits in with your lifestyle.

For your overall health, it’s important that the eating plan is balanced – low in saturated fat, salt and sugar and contains all the essential nutrients and fibre. And, regular exercise is good for both your waistline and health – especially your heart.

Just a few of the eating plans or ‘diets’ for weight loss have undergone rigorous research to determine whether they are safe and effective for people with diabetes. Most of these weight loss diets that have evidence for use in diabetes have been studied in people with Type 2 diabetes.

Low fat, healthy balanced diet

This is the conventional healthy, balanced diet that involves eating foods from all the five food groups. You’ll eat more fruits and vegetables, some starchy carbohydrates, proteins and dairy but limit the amount of fat you eat.

The main principle of low fat diets is that, gram for gram, fat contains more calories than any other macronutrient – so by reducing your fat intake you’ll reduce your calorie intake, too. However, it is not that straightforward. If you replace your fat with larger portions of starchy foods, you are less likely to derive much benefit. Therefore, it is important to look at your overall portion sizes and try to reduce portions of other foods, as well as the fat. Try replacing some of the reduced portions with more fruits and vegetables, which are generally lower in calories, so that you don’t feel hungry.

Try these other ways to reduce fat in your diet.

  • Limit the use of oil in cooking.
  • Opt for reduced-fat or low-fat alternatives for dairy and pre-packed foods whenever possible.
  • Read the labels on pre-packaged food – if the fat per portion is red, choose something else.

There’s been extensive research into low fat diets, which has shown that this approach can help you to lose weight, control your HbA1c and reduce your cardiovascular risk factors. There is also evidence that the positive changes gained from this dietary approach can be maintained for over four years.

Low carbohydrate diet

There are several versions of a low carb diet. The general principle of a low carb diet is to limit the amount of carbohydrates you eat, and to get more of your calories from proteins and fat.

Practical ways of doing this include making sure that the limited carbohydrates you include in your diet come from good sources, like fruits and vegetables, pulses, dairy and wholegrain options of starchy foods, rather than foods laden with unhealthy fats and sugars like cakes, biscuits, pastries, and fizzy drinks. You will not derive enough benefit from a low carb diet if you replace your carbohydrates with too much fat.

Since the amount of carbohydrate has the biggest effect on blood glucose levels after eating, many people with diabetes need to have some level of carbohydrate restriction. Review of evidence shows that low carb diets can help people with Type 2 diabetes lose weight and improve blood glucose control.

If you treat your diabetes with insulin or any other medication that puts you at risk of hypoglycaemia (low blood glucose levels), following a low carb diet may increase this risk. However, your diabetes team can help you adjust your medications to reduce your risk of hypos.

Very low calorie diet

Very low calorie diet (VLCD) involves restricting your daily calorie intake to fewer than 1,000kcal a day, and in some cases between 450 and 800kcal a day. This is achieved through usual foods, liquid foods (proprietary formula) to replace meals or a combination of the two.

If you choose a very low calorie diet, meal replacement products are available to buy as ready-made milkshakes or powdered milk that need some preparation, snack bars and soups. If you decide to use any of these products for total meal replacement, make sure that the product you buy provides all the essential nutrients in the stated servings. If you are doing a partial meal replacement, try to eat more fruit and vegetables as part of your meals, to make sure you’re getting enough fibre.

There is evidence that VLCLD significantly improves HbA1c and results in weight loss in people with Type 2 diabetes. You might have heard more about these diets recently, with results of a small study reporting possible reversal of Type 2 diabetes in people who consumed 600kcal/ day for 8 weeks. However, the researchers are currently undertaking a larger study to better understand how the results can be replicated in real life.

Because this is a restrictive diet, it is not recommended in the long term – generally up to 12 weeks. You’ll need medical supervision to make sure that you’re getting all the essential nutrients you need. If you’re on insulin or certain diabetes medications, you may also need support to adjust your medications to prevent hypos. You might also need to test your blood glucose more often.

Mediterranean diet

This is a diet largely based on plant foods and includes a lot of vegetables, beans and pulses, nuts and seeds, wholegrain breads and pasta, and olive oil. It also includes some dairy (milk and yogurts), eggs and fish in moderation. Red meat and processed foods are usually avoided, and wine is included in moderation.

Although the majority of studies on this diet have taken place in Mediterranean countries, there is evidence that the Mediterranean-style diet can promote weight loss, improve blood glucose control and help reduce cardiovascular risk in people with Type 2 diabetes.

Low Glycaemic index (GI) diet

Glycaemic index is the ranking of carbohydrate-containing foods based on their immediate effect on blood glucose levels. Foods that break down slowly are assigned a lower GI, and these are deemed to be better for you, especially as they tend to raise blood glucose levels slowly.

People who follow a low GI diet, opt for carbohydrate-containing foods that have a low GI. Several reviews have concluded that this dietary approach improves blood glucose control in people with diabetes as well as helps to reduce cardiovascular risk. Although there is some evidence that low GI diet can promote weight loss in people without diabetes, the evidence for weight loss in people with diabetes is insufficient.

Other diets

There are other popular diets like the Intermittent fasting (e.g. the 5:2 diet) and the Paleo diet etc. These diets have not been included here because there is not enough evidence for their use in people with diabetes.

Whether you choose to try one of these eating plans, or another type of diet, it’s essential that you discuss your plans with your diabetes team. They can make sure you have the right information and the support you need to be successful with your chosen weight loss plan.

Visit www.diabetes.org.uk for more support and information about diabetes, great tasty recipes and healthy eating tips.

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Last revised: 22 December 2017
Next review: 22 December 2020