This 2009 review briefly summarizes the potential impact of very low-calorie diets (VLCDs) on diabetic patients. VLCDs generally involve intake of 450 to 800 calories per day. The diets are often ketogenic in practice, due in no small part to the significant carbohydrate restriction required to meet caloric targets while maintaining sufficient protein and nutrient intake. While VLCDs historically have often introduced nutrient insufficiencies, modern dietary strategies and supplements have reduced the risk associated with VLCDs and increased the ease of adherence to such diets.
The authors note the limited body of evidence supporting VLCDs as a weight-loss intervention, particularly within diabetic populations. This literature deficit is why multiple groups (including the International Diabetes Federation and a Cochrane Review) produced statements recommending diabetics avoid using VLCDs. However, these cautionary recommendations fail to account for the potential of VLCDs to affect glycemic control independent of any effects on weight.
As summarized in Figure 1, VLCDs have been shown to have rapid and substantial beneficial effects on glycemia in diabetic subjects. A VLCD (which, as noted above, requires significant restriction of both calories and carbohydrates) will quickly deplete glycogen stores in both the liver and muscle, and subsequently induce ketosis. This reduces glucose production and secretion by the liver, lowering blood glucose levels. Over time, insulin resistance in the liver and muscles dissipates as the fat stores in these organs are reduced. The diet may also increase pancreatic insulin sensitivity through mechanisms related to and independent of ketosis. Finally, the ketogenic state improves satiety, which leads to greater dietary compliance.
At the time of this review’s publication, much of this research on VLCDs was preliminary; as other posts on CrossFit.com have shown, subsequent research has demonstrated substantial practical benefits from the use of VLCDs in diabetic subjects.
Editorial note on potential conflicts of interest: The senior author on this publication is Chair of the Medical Advisory Committee on Optifast, a company that produces shakes to be used in or as VLCDs.
Comments on Effects and Clinical Potential of Very-Low-Calorie Diets (VLCDs) in Type 2 Diabetes
I see that very low-calorie diets have their use. They are also called fasting-mimicking diets because the caloric intake is so low. The argument is that they have the same physiological effect as fasting, but are more sustainable. I think that it must be tough to meet the nutrient requirements on such a low-calorie diet, so I doubt it's sustainable long-term. Fasting periods that are limited in time and alternate with nutrient-rich feasting periods might be a good alternative.
Agree with both the positive and negative points here, though I understand "fasting mimicking diets" to generally refer to a specific sort of VLCD.
What this, and some of the other posts on Crossfit.com, have tried to allude to is the targeted potential of VLCDs to drive rapid improvements in metabolic health in a way less intensive dietary interventions can't. Effectively, some sort of VLCD or a well-designed fast seems to be able to move a lot of organs in a healthier direction - clearing out fat in the liver and muscle, improving insulin sensitivity and pancreatic insulin response, etc. In individuals who want or need to quickly improve their metabolic health, a temporary VLCD, followed by a more sustainable healthy diet, may be a uniquely effective course of action. It's also interesting to think about the ways the specific metabolic benefits of a VLCD could be captured over the longer term - both specific diets like Valter Longo's specific "fasting mimicking diet" and more general diets like a ketogenic diet seem to hold some, if not all, of the same benefits.
All tools which can be used to bring us from one state of metabolic health to another.
agreed sarah, i see them more as a hack or bridge to fasting. another issue with the very-low-calorie diets is that, if used over the long-term without refeeds, they will lower BMR a la Biggest Loser - and we all know how big of a fiasco that was for participants
Effects and Clinical Potential of Very-Low-Calorie Diets (VLCDs) in Type 2 Diabetes
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