Very Low Calorie Diets And Diabetes

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Most of us know that losing weight by conventional diet and exercise plans is difficult, and just as many of us know that keeping that weight off in the long term through diet and exercise alone is almost impossible. This is not a new concept – about fifty years ago a Dr Stunkard who was working with obese people made a landmark statement that has been quoted in every lecture on obesity that I have ever attended: ‘Most obese persons will not stay in treatment of obesity. Those that stay in treatment, most will not lose weight, and of those who lose weight, most will regain it’. This was certainly true when he said it, and remains so to a certain extent today, and one of the threads running through the whole Stop Dieting, Start Living philosophy is based on this truth –diets usually don’t work.

The medical profession has known for a long time that for most people with heart disease or diabetes, losing 5-10% of their total body weight will greatly improve their condition, and a combination of fairly intense education and monitoring of peoples diet and exercise behaviours can achieve this sort of weight loss in a group of sufficiently motivated patients. The problem is exactly as Dr Stunkard predicted – most of these people regain the weight they have lost in only a few years, although research has recently suggested that even yo-yo dieting, although not ‘good for you’ (see the Stop Dieting Start Living book for details about this), is better than being resigned to a state of permanent overweight or obesity.

For some extremely overweight people with urgent health needs it is clear that simple diet and exercise change is not going to be sufficient, either because the total weight loss will not be enough, or it will not happen quickly enough. The current trend in the UK is to offer these people bariatric surgery, that is gastric banding or bypass surgery, and I have covered this in another article – essentially, gastric bypass is particularly effective but comes with significant risk to life and health, and while it will result in more weight loss than any other currently available intervention when the right person has the right procedure at the right time, it is not an easy way out and should be considered as a last resort for most people.

So what about the many people who find themselves in the wilderness, being heavier than those just needing to shift a couple of pounds to tweak their blood pressure and waist circumference a bit for medical reasons (and should do fine with a well designed diet and exercise plan or living a Spirit led lifestyle), but not carrying enough excess weight to justify the significant risks associated with gastric bypass surgery? One option available to them is the Very Low Calorie Diet or VLCD.

VLCDs are not so much a diet as a medical intervention. Usually they take the form of liquid meal replacement with a small amount of solid food added in and involve a lot of supervision by a specialist doctor or dietician and last for a period of 8-16 weeks. They have traditionally involved eating 400-800 calories per day, although recent evidence has shown that people eating 400 calories per day do not lose any more weight than those eating 800 calories per day, so most people are no longer asked to reduce their calorie intake to less than 800 calories per day. This is not as harsh as it sounds, and thankfully one of the side effects of VLCDs is a reduction in appetite so hunger is not as much of a problem as you might expect.

We have known for some time that VLCDs can greatly benefit people with type 2 diabetes because their body responds more efficiently to their own insulin afterwards. Some of them can stop their medication, and their blood pressure and cholesterol and various other issues associated with heart disease improve, and most of the benefits begin before much weight is lost, suggesting that the lack of calories is having another effect as well as the weight loss. At this point nobody knows for sure how VLCDs improve diabetes, but there are a number of theories about this and there is a great deal of ongoing research in this area. One study that was published a few weeks ago found that people on a VLCD had considerably less fat in their pancreas (the organ that makes insulin) after a number of weeks, and the authors have suggested that removing the fat from the pancreas may take the strain off the pancreas and enable it to produce insulin more efficiently. Other researchers have suggested that the liver may be involved and that the VLCD may improve the way that the liver deals with sugar. We do know that not everyone with type 2 diabetes will benefit from a VLCD – those who have been diabetic for a long time do not seem to improve as much as newly diagnosed diabetics, and those with very little ability to make insulin also do less well.

So what about weight loss? Some people manage to lose 35kg, that is about 5 stones, in their 16 weeks on the VLCD in comparison with about 5kg on a conventional diet and exercise plan. So there is no doubt that VLCDs make you lose weight!

One of the big questions relates to whether these people can keep the weight off in the long term, and it seems that many of them can. In one study, 18 people with diabetes followed a VLCD plan for 4 weeks and then were reassessed a year later. 13 of them had stopped needing insulin and had regained a small amount of weight, but had kept a significant proportion of their weight off. The 5 people who were back on insulin had also regained most of their weight although they still had lower blood pressure and cholesterol levels than before the diet. Other studies have also found that more people maintain their weight loss long term following a VLCD than most other weight loss plans.

Would I recommend a VLCD as a weight loss method? If you need to lose a lot of weight quickly for medical reasons, for example if your diabetes is out of control or in preparation for important surgery, then your doctor may well recommend a VLCD and I think this would be very reasonable. If you are contemplating one of the commercially available VLCDs such as LighterLife then I would be more hesitant. They certainly have their place but there are good reasons why you have to have your doctor’s permission before joining up – there are a number of risks associated with VLCDs, so do take thorough medical advice before you proceed.

Lastly a word about calorie restriction. This is very different from VLCDs and is based on evidence that people who restrict their calorie intake to significantly less than the government recommendation in the long term tend to lead longer, healthier lives. I have covered this in another article on this website so will not repeat it here, but the whole concept is very interesting food for thought.

Essentially VLCDs have clear benefits as a form of treatment when the right person follows them at the right time, but for most people they are thankfully not necessary and the ‘Stop dieting, Start living’ philosophy is more appropriate, more tasty and more fun!


  1. Trish on April 6, 2015 at 5:59 pm said:

    As well as diabetes type 2, I also have hypothyroidism. Is this ok on a vlcd? I do not feel hungry on this diet. But can I still do all 3 meal replacements, and nothing else? Or, is this too much. As far as I know this is safe. Also I am having trouble sleeping on this diet. Is this one of the side effects? Trying to give up the ciggies too. It sounds a lot to do at once. But I feel the timing is right. And I am ok with it. Thanks for your help TRISH.

    • Sue Kenneally on April 25, 2015 at 3:39 pm said:

      Hi Trish,

      Sorry for the delay in replying, I had two weeks off over Easter and it has taken a while to catch up with emails etc. It’s difficult to comment in too much detail as I don’t know you, but in principle you should be fine on a vlcd with diabetes and hypothyroidism. A few people do mention difficulty sleeping but I gather that this improves eventually. Good luck quitting smoking – how are you doing that? Your GP can prescribe you lots of things to help and it is quite likely that there is an NHS support group near you. Let us know how you get on! Sue K, F4LF GP

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