Rapid Weight Loss Diets and Severe Calorie Restriction

Very Low Calorie Diets (VLCD) and Low-Fat Low-Carb Diets

  • we have been blinded by our focus on weight loss
  • fasting, very low calorie diets and similar brief, dramatic changes in food intake may by far have their most important use in treatment of metabolic syndrome and metabolic disease – such as type 2 diabetes and fatty liver

Even in terms of weight loss, the calorie level may be a distraction and a blind-end. Can we learn how to go from the brief and readily-lost weight-reduction benefits of short-term severe calorie restriction to something that is useful for weight control long-term? Simply sustaining a fast or very low calorie intake indefinitely is not an option. Are there aspects of what is going on during such an severe dietary intervention that can be understood and carried on even when the food intake returns to an amount to sustain health and body weight? I think the most promising things to consider are:

  • if someone with insulin resistance has a substantial improvement in insulin resistance (and maybe even pancreas health) during the treatment phase, maybe the right thing for them is to shift to a pattern of food intake that does not impose a high or sustained demand for insulin – so that the insulin they are producing is enough for their metabolism to run well.
  • someone with “metabolic inflexibility” – meaning that their cells are impaired in the ability to shift between the two main fuel streams of glucose and fat/ketones – may do best continuing an eating pattern that keeps the body ready to switch on a daily basis into periods of fat-dominant metabolism – such as longer over-night fasting periods (e.g. 10-12 hours) and/or periods of sustained exercise that out-strip glucose supply and/or use of intermittent-fasting periods as individually needed over time
  • recognizing that most of the people under severe calorie restriction will have shifted to being in a state of ketosis – either steadily or intermittently within each 24-hour period. If the calorie intake is low enough, ketosis will result even if there is no specific focus on eating “low carb”.  Over some weeks they will have adapted to this new state. If a particular person thrives in this state, they can learn how to eat in a long-term, sustainable and enjoyable way while maintaining whatever degree of ketosis suits them (continuous or intermittent). We have largely been blind to this phenomenon and I think many people who report that they “feel great” under rapid weight-loss conditions (especially those who have a very bad experience soon after returning to a higher food intake) would be well-served by this strategy.
  • this is one of many types of weight-loss interventions that could be expected to cause major changes in the gut microbiome. For those people who have some sustained benefit, maybe changes in the gut microbiome are involved? So far, we do not know what to do with this possibility – in terms of how to test or treat an individual. Plenty of people and companies are busy making one recommendation or another, but so far it is all premature, despite the money they may be bringing in.
  • maybe some people who have more lasting benefit from such treatment periods do so related to having a “gut holiday” or drop in inflammatory products reaching the liver or via effects on the vagus nerve, or? or?

For me, it is particularly upsetting when I am speaking with someone who has done very well with a very low calorie program, and then rebounded relentlessly when they stopped the program – who was never given the information that they were in an adapted state of ketosis and never instructed on how to continue that as an ongoing lifestyle if it suited them.

There are endless versions of very low calorie diets. Some may be labelled as such, but most often they are disguised under other names. You may have been on a VLCD without knowing it. That commercial weight-loss centre or that diet book you may be considering might be suggesting a VLCD.

The main points of interest and concern:

  • when calorie intake drops, it is more and more unlikely that what is eaten will supply all the needed nutrients
  • even when only high quality foods are chosen, below a certain amount of intake it is just not possible that all the necessary vital nutrients will be provided in the food
  • there is loss of muscle tissue, which can be lessened but not completely prevented by a higher protein intake and exercise
  • for people with certain medical problems, and for people on a number of commonly-used medications, a major change in diet can cause medical problems that are potentially severe
  • very low calorie diets are a pretty obvious thing to think of when weight loss is the target, so it has been tried endlessly (I would think many millions of times) and studied in research trials. Of course it is effective short-term. However, like all interventions that impose a calorie-intake restriction, the long-term results are poor. A small percent of people do well when looking at the outcomes 2-3 years later.
  • there is concern that such severe dieting can precipitate the development of eating disorders
  • despite this, the world is so desperate for effective ways to achieve weight loss, there is a relentless effort to re-visit the topic
    • much of this is just to find ways of marketing the quick weight loss effect, while dressing it up as some new approach
    • some of this is a legitimate attempt to find some way to make the benefits sustainable

What is “very low calorie”? Of course, in real-world-impact that depends a lot on the person. One person’s basal need for calories for a minimally-active day may be 1300 calories and another person’s need for calories for an average physically-active working day may be 3000 calories. So, what is very low calorie is only truly meaningful when considered in terms of the individual and their current circumstances (where have you heard that before?).

For purposes of discussion, in medicine the term Very Low Calorie Diet is generally meant to refer to a diet of 800 calories or less. Obviously that is an arbitrary cut-off. There is not much meaningful difference in practice between an 850 calorie diet and an 800 calorie diet. So, the term is counter-productive as a tool used in discussion unless we remember that it has limited meaning. The number of calories might be much less than 800 calories.

For fasting and near-fasting (for example, including some broths or low-calorie vegetables in soups), we generally don’t use the term VLCD.

Similarly, we don’t tend to use the term VLCD in relation to alternate day fasting or intermittent fasting, even though some days the person is truly fasting or is having a low calorie intake. For example, some programs that are described as “alternate day fasting” actually include significant calories on the “fasting” day, such as 400-500 calories – so that day would class as a “very low calorie” day. It is becoming clear that the body has very different adaptations to intermittent and brief changes in calorie intake versus day-by-day longer term changes.

Some Examples:

Programs focused on weight loss:

(1)  In the Vancouver area, a certain brand-name low-fat, low-carbohydrate diet is prominent. Of course they do not describe the calorie intake, but the participants are expected to shift into ketosis and I expect that a simple tracking of their calories would reveal that most are at about 800 calories or less.

It is simply a fact that a diet that is both low fat and low carb will be low in calories and not a sustainable option long-term. So, eventually the person has to start adding more food back. In my experience in interviewing some of their previous clients, none have been taught about nutritional ketosis or given the info on how to maintain the ketosis state while shifting to a slower weight loss or a weight maintenance phase long-term. Nor, in my experience, are they taught how to eat in a way that does not over-load their particular insulin function capability.

(2) The Dukan Diet

(3) Most versions of the “HCG Diet”

Programs focused on metabolic health:

(1) The “Newcastle ” study by Professor Roy Taylor

*** Please do not do this at home without first discussing it with your personal physician for medical review and support ***

Important: Although it is very promising, I would not generally advise this particular program as in my opinion there are better options. I include the information here as it contributes to our over-all thinking about metabolic health and type 2 diabetes and demonstrates a different approach to thinking about the power of dietary interventions.

This is a very small study and subject to a lot of debate and criticism. The importance of this small, exploratory study is in testing a concept.

A lot of attention is being paid to the recent findings that weight loss surgery can have profound benefits in type 2 diabetes – more rapidly than the amount of initial weight loss was thought to explain and not as dependent on the degree of weight loss as expected. This has been part of a shift in thinking about these types of surgery as “metabolic surgery” instead of as “weight loss” surgery.

Professor Taylor wondered if those same benefits re: type 2 diabetes could be achieved without the surgery.

Notes: This was a formulated liquid diet of 600 calories, including vitamins and minerals in the formula. Part of the recommended program was added vegetable salad or soup three times a day – bringing the total calories to 800 calories a day. For gut microbiome theorists – this means that there was no fibre other than vegetable fibre.

Information on the study, along with supportive materials:  LINK

Commentary: “Can you really ‘reverse’ Type 2 diabetes by eating no more than 600 calories a day? The Newcastle study sparked a huge debate when it was released earlier this year. Caroline Wood asks two top New Zealand experts what they think.”  LINK  This is a very interesting commentary and worth reading full (except note that the diet was 800 calories/day, not the 600 cal/day as described in that headline). Here is a quote:

“Researchers think the extreme diet and accompanying weight loss helped people with Type 2 diabetes ‘wake up’ the insulin-producing cells in their pancreas.

Sticking to the strict 600 calorie a day diet causes fat levels in the pancreas to drop rapidly, restoring normal function, believes Professor Roy Taylor, who conducted the Newcastle University study in England.

Dr Paul Drury, Clinical Director of the Auckland Diabetes Centre and Medical Director of the New Zealand Society for the Study of Diabetes said: “It’s an extremely important study. It’s one of the best pieces of science that has been done in a long time. It was an attempt to show you can do bariatric surgery without the bariatric surgery and get the same results.”