How long can I stay on a low-calorie type 2 diabetes diet?

Implementing a low-calorie diet is one of the most effective ways of reversing type 2 diabetes. But what is the recommended duration for a low-calorie diet?
Simon Lovick
min read
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Quick summary

  • An 800kcal eating approach is a proven method for weight loss.
  • Understanding the timeline of type 2 diabetes reversal, and where a low-calorie diet fits into this—including how long it takes to have the desired effect.
  • How to transition back into a normal 2000kcal a day diet.

Dieting is one of the most hotly debated topics in the world of healthcare and wellbeing. 

It seems like, on a nearly monthly basis, new diets are introduced by fresh-faced experts proclaiming the benefits of their specific eating recommendations, all based on some dubious scientific evidence. With so many diets out there, it’s hardly surprising consumers are overwhelmed by choice and frequently misled. 

At Habitual, we truly believe that our approach to food is one of the key factors in reversing type 2 diabetes. There’s a strong correlation between certain diets, such as 800kcal programmes and total diet replacement, and the weight loss that can help put type 2 diabetes into remission

What’s not always clear, however, is how long a diet should last. With no clear endpoint, dieting can feel limitless or even pointless, not to mention unhealthy. That’s why we’re revealing our recommended length for dieting and our tips for sustaining a healthy eating lifestyle even after your diet stops. 

What is a low-calorie diet?

While there are a number of diets which can help you achieve type 2 diabetes reversal, we believe that reducing your daily calorie intake to 800 is the most effective method. So what do we mean by that?

On the one hand, it really is as ‘simple’ as it sounds—rather than eating the recommended 2000kcal a day, you eat 800kcal a day. How you make up this 800kcal is up to you but remember: the most effective way to lose weight is the way that suits you and that means your budget, your preferences, your daily routine, and your goals. 

It may suit you to build an 800kcal day out of whole food, cooking three low-calorie meals for breakfast, lunch, and dinner. Alternatively, you may find it easier to combine low-calorie cooking with meal replacements. The most effective method, however, and we’re saying this based on both rigorous scientific evidence and our own experience, is total diet replacement (known as our 4/day programme).[1]

Low-calorie meal replacement diets are the best way to lose weight with type 2 diabetes

Churuangsuk et al., Diabetologia

Total diet replacement, or TDR, is the method by which you completely replace your ordinary diet with nutritional meal replacements that provide you with your required nutrients for each day but with a much lower calorie content. You may recognise brands like Huel and Slimfast, each offering different forms of meal replacement that can help you achieve weight loss. At Habitual, we have our own range of total diet replacement meals, which form the backbone of your weight loss programme: these include different shakes, soups, and porridges packed full of vitamins, minerals, and nutrients. 

Note, there is a difference between standard meal replacement products and total diet replacement products. Total diet replacement products have to meet certain micro and macronutrient levels—ours meet those set by EU regulations. In comparison, meal replacements don’t have to meet these levels, meaning they can contain insufficient nutrients to wholly replace a diet.

Through a low-calorie diet, you’ll be consuming a much lower daily intake of calories—the ultimate goal behind this is weight loss and for many, achieving the average weight loss target of 15kg has a proven scientific link to putting type 2 diabetes into remission.[2] 

An average weight loss of 15kg can help put type 2 diabetes into remission

Lean et al., Lancet Diabetes Endocrinol

Going from 2000kcal to 800kcal might seem like a big jump, so you may be asking: is this safe? In short, yes. When following a guided programme such as Habitual, you’ll still benefit from a nutritionally well-rounded diet, while consuming far fewer calories. That said, if you have a high BMI (over 40), then it’s recommended that you taper your diet down to 800kcal, rather than jumping straight into it.

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How long should a low-calorie diet last? 

Following an 800kcal eating approach is a significant lifestyle change. For many, this may seem overwhelming, but how long should it last? 

In our type 2 diabetes reversal programme, eating 800kcal a day lasts 12 weeks. This is not just the Habitual recommendation, this is what the NHS also recommends and is the duration of their fairly new low-calorie diet treatment for type 2 diabetes.[3] 

12 weeks on 800kcal is generally enough time to achieve significant weight loss


So why is this? Well, 12 weeks or 3 months on 800kcal is roughly enough time for you to achieve significant weight loss, which as earlier outlined, is the target for putting your type 2 diabetes into remission. 

What is eating 800kcal a day really like?

Well, at first, it may be difficult. You’re likely to feel hungry a lot of the time (although often this can be confused with thirst, so make sure you’re drinking lots of water). You also may feel dizzy or irritable for the first few days. After a few days/weeks, though, your body should get fairly used to your new diet. You will reach a mild state of ketosis, making you feel fuller and enabling your body to survive off far fewer calories. 

It’s not an exact cut-off, but any longer than 12 weeks and your body may start to see negative effects. The target should be on a sensible weight loss goal as opposed to excessive weight loss, which may start to cause additional problems to your body. After 12 weeks, you should start to transition out of the 800kcal eating approach into a more sustainable eating approach for your body. 

What should I do after the low-calorie diet?

So what happens after the 12-week low-calorie diet ends? Does everything go back to normal? 

Not exactly, no. One of the main risks with following a low-calorie diet and total diet replacement—and often one of the biggest criticisms levelled at it—is that you can quickly pile the pounds back on after it finishes. This is because your body has been used to eating a much lower level of calories and needs to be gradually reintroduced back to the recommended level of 2000kcal a day. This is critical—sustaining your weight loss is a key factor in ensuring that your type 2 diabetes stays in remission.  

During the Habitual type 2 diabetes reversal programme, we recommend a 4-week period of ‘health maintenance’, gradually moving off the low-calorie eating approach that will have formed the backbone of your diet for the past 12 weeks, and back into eating more regular food. At the end of these 4 weeks, you should be back to eating around 2000kcal a day. 

There are some good ways to achieve this transition back into eating normally:

  • Plan your meals in advance—have a calorie goal in mind for each meal in advance, rather than counting retrospectively. This will ensure you are transitioning methodically and avoiding the risk of overeating
  • Plan when you are going to eat—this should help avoid snacking and overeating
  • Keep track of what you are eating in a journal or food diary
  • Delay the reintroduction of things you really crave—this will help you avoid things that might trigger you to overeat

Even after those 4 weeks, though, not everything should return to normal. Your unhealthy eating habits prior to starting a low-calorie diet may be one of the biggest risk factors to your type 2 diabetes condition, and therefore shouldn’t be reintroduced post-diet. You should focus instead on building a healthy lifestyle for yourself, based on eating more responsibly alongside a good exercise regime of around 30 minutes exercise a day, five times a week. 

Intermittent periods of total diet replacement can help maintain weight loss in the long-term

Christensen et al., Am J Clin Nutr

You also may decide that you want to go back onto the low-calorie diet, again, for a maximum of 12 weeks. There’s actually strong evidence to suggest that following this approach intermittently—for example, 3 weeks of total diet replacement every 3 months—has strong benefits and can help you maintain weight loss in the long term.[4]

of A lot of the bad press around dieting comes from the fact that it can be temporary and fleeting—hence terms like ‘fad’ diets or ‘crash’ diets. Good dieting, however, is a longer-term commitment to eating more healthily and balancing more ‘total’ approaches like 800kcal programmes or total diet replacement with healthy, well-rounded nutrition. Adopting this mindset will be instrumental in pursuing type 2 diabetes reversal. 


[1] Churuangsuk, C., Hall, J., Reynolds, A., et al. (2022). Diabetologia 65:14-36. Accessible here.

[2] Lean, M.E.J., Leslie, W.S., Barnes, A.C., et al. (2019). Durability of a primary care-led weight-management intervention for remission of type 2 diabetes: 2-year results of the DiRECT open-label, cluster-randomised trial. Lancet Diabetes Endocrinol 7(5):344-355. Accessible here.

[3] Low calorie diets to treat obesity and Type 2 diabetes. NHS UK. Retrieved 24 October 2022. Accessible here.

[4] Christensen, P., Henriksen, M., Bartels, E., et al (2017). Long-term weight-loss maintenance in obese patients with knee osteoarthritis: a randomized trial. Am J Clin Nutr. 2017 Sep;106(3):755-763. Accessible here.

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