Dr. Sharma's Obesity Notes

Following yesterday’s Obesity Fact #3 (exercise is good for you even if it doesn’t help you lose weight), Obesity Fact #4 from the New England Journal of Medicine paper, states that,

“Physical activity or exercise in a sufficient dose aids in long-term weight maintenance.”

This is a pretty well-established fact, however, the authors hasten to point out that the key term in this “Fact” is the term “sufficient dose”.

Thus, the authors note that,

“Physical-activity programs are important, especially for children, but for physical activity to affect weight, there must be a substantial quantity of movement, not mere participation.”

Indeed, recent studies have questioned whether in fact, the amount of physical activity that is achievable in school phys-ed programs (for example) would provide a sufficient dose to prevent weight gain (let alone maintenance of weight loss).

Thus, this “Fact” reflects the consistent body of knowledge that exercise as a way to control your weight, be it to prevent weight gain, lose weight, or prevent weight regain, requires a substantial dose of activity – more than is perhaps necessary to simply maintain good health (see Obesity Fact #3).

As I have said before, exercise is perhaps best seen as part of energy-in rather than energy-out and the right dose of exercise to help you control your weight is just the amount that it takes to RUIN your appetite. For some people that may well be the benefit you get from walking your dog.

AMS
Edmonton, AB

Continuing in my discussion of obesity myths, presumptions and facts published recently in the New England Journal of Medicine, we turn our attention to obesity presumption #4:

“Weight cycling (i.e., yo-yo dieting) is associated with increased mortality.”

This presumption is based on the observation that,

“In observational studies, mortality rates have been lower among persons with stable weight than among those with unstable weight.”

Again, we are reminded that correlations do not prove causality and it is easy to imagine all kinds of confounders and other factors that could lead to finding such a correlation.

But, not only, is this a finding that has has not been confirmed in several more recent large epidemiological studies, as the authors point out, there is also little support for this idea from experimental animal studies – intentional weight cycling has simply not been shown to shorten life spans.

Indeed, regular readers may recall my more recent post showing that that short-term weight cycling does not appear to have consistent adverse metabolic effects.

However, as I have pointed out, irrespective of whether or not yo-yo dieting shortens your life span or increases your risk for cardiovascular risk factors, the emotional impact of repeatedly losing weight only to put it on again may not exactly be conducive to good mental health and quality of life.

It is certainly easy enough to see why people who manage to maintain their weight constant, rather than losing weight just to regain it, may well end up being healthier (and happier?) in the long run.

AMS
Edmonton, AB

The 3rd Obesity Presumption in the New England Journal of Medicine on obesity myths, presumptions and facts paper states that,

“Eating more fruits and vegetables will result in weight loss or lessweight gain, regardless of whether one intentionally makes any other behavioral or environmental changes.”

The notion underlying this presumption is the common belief that,

“By eating more fruits and vegetables, a person presumably spontaneously eats less of other foods, and the resulting reduction in calories is greater than the increase in calories from the fruit and vegetables.”

While this may well be the case for some people, unless those fruits and vegetables are being eaten raw, chances are that they may well be contributing a significant amount of calories to your diet (think Indian vegetarian curry or a vegetable stir-fry).

It is therefore by no means surprising that simply going vegetarian (or even vegan) will do much for your weight even if it may take longer to eat the same amount of calories.

Thus, the studies quoted in this paper failed to find any impact on body weight by simply increasing fruit and vegetable intake without making any other adjustments to your diet – in the end what counts with regard to body weight are calories – irrespective of whether these are derived from vegetables, fruit, fats, oils, carbs, meats, dairy or alcohol.

If anything, this presumption should serve to remind us that eating healthier food is not the same as eating fewer calories.

AMS
Edmonton, AB

Myth #4 addressed in the recent New England Journal of Medicine article on obesity myths, presumptions and facts is:

“Assessing the stage of change or diet readiness is important in helping patients who seek weight-loss treatment.”

This myth alludes to the use of Prochaska’s transtheoretical model of Readiness for Change, which identifies various stages beginning from precontemplation, to contemplation, to preparation, to action, to maintenance (some authors also include a stage of relapse)

With regard to this “myth”, the authors note that

“Readiness does not predict the magnitude of weight loss or treatment adherence among persons who sign up for behavioral programs or who undergo obesity surgery.”

In support of this being a “myth”, the authors quote five trials (involving 3910 participants; median study period, 9 months) that specifically evaluated stages of change (not exclusively readiness) and showed an average weight loss of less than 1 kg and no conclusive evidence of sustained weight loss.

As a possible explanation for this finding the authors offer:

“…people voluntarily choosing to enter weight-loss programs are, by definition, at least minimally
ready to engage in the behaviors required to lose weight.”

I would take a somewhat different view of this based on my own experience with assessing readiness for change.

There is no doubt that someone, who is not ready, is unlikely to be successful at losing weight and keeping it off. It certainly takes more than a “pre-contemplator” or “contemplator” or even someone, who is in “preparation” to actually begin doing something that will affect their weight – thus, by definition, anyone, actively trying to lose weight is already in the “action” phase. (I have never met a pre-contemplator who agreed to undergo bariatric surgery).

The real question is therefore whether or not being in the “action” phase will predict outcomes. Here, of course the answer is no.

Just because you are actively doing something to manage your weight (action stage) does not mean that you will be successful – after all, the vast majority of people, who try to lose weight, ultimately fail to keep it off.

Thus, it is easy to see why there is little relationship between Stages of Change and outcomes, when one considers all comers.

This, however, in clinical practice is not really the point of assessing readiness.

Rather, the clinical utility of this framework is to assess whether or not someone is even close to embarking on any kind of weight management and moving them along this continuum if they are not.

While being in the action stage does not guarantee success, being a pre-contemplator, contemplator, or even preparer, virtually rules it out.

Were you to liken success in losing weight to winning a lottery, the person in the action phase at least bought a ticket (the others are still only thinking about buying one). I know of no lottery that you can win if your don’t buy a ticket.

Yet, if I were to study the chances of winning a lottery, it may well be hard to prove that buying a ticket actually increases your chances of a win. (Imagine a lottery where the chances of winning are one in a million and we compare the odds of winning amongst two million people randomised to either buying a ticket or not. We will end up with one winner in the ticket group and no winner in the no-ticket group – not enough to statistically prove that buying a ticket increases your chances of a win. Yet, we would all agree that not buying a ticket virtual guarantees not winning – statistics or no statistics!)

Although, the odds of losing weight and keeping it off may be far better than of winning a lottery, it is still a rather rare event.

Thus, while I agree with the authors that simply being ready may only marginally (if at all) increase your chances of success, I can assure you that not even thinking about it virtually guarantees failure.

This is why, I believe that a conversation about readiness is a sensible conversation to have with anyone wondering about their weight (by definition, this would already be a contemplator).

AMS
Edmonton, AB

Continuing in my discussion of the obesity myths, presumptions and facts, published recently in the New England Journal of Medicine, today’s myth is about the rate of weight loss.

As the authors put it:

“Large, rapid weight loss is associated with poorer long-term weight outcomes than is slow, gradual weight loss.”

This “myth” is attributed to

“…a reaction to the adverse effects of nutritionally insufficient very-low-calorie diets (<800 kcal per day) in the 1960s; the belief has persisted, has been repeated in textbooks and recommendations from health authorities, and has been offered as a rule by dietitians.”

This reaction would be no surprise, as in those days, the very-low-calorie diets due to inadequate protein content (and perhaps a few other nutritional deficiencies) did result in rapid loss of lean tissue, thereby reducing metabolic rates beyond what may have been expected with a more gradual nutritionally balance weight loss.

In contrast, today’s low-calorie formula diets are generally high in protein and nutritionally balanced (except perhaps for fibre) and have in fact been shown in some cases to preserve lean body mass compared to simply eating less.

As regular reader of these pages may recall, I have previously written about situations where rapid weight loss with the use of low-caloric diets (900 Cal/day) may be indicated and in fact beneficial for patient management.

Nevertheless, as the authors point out, when comparing longer-term outcome data (a couple of years and beyond), it does not appear that people, who lose large amounts of weight rapidly have any less (or greater) chances of keeping weight off, than those who lose weight slowly.

Obviously, as with any diet, the ultimate question is really, whether or not patients can live on a restrictive caloric intake (and a rather high amount of physical activity) in the long-term.

As I recently pointed out in my discussion of the findings of the National Weight Control Registry, maintaining a significant amount of weight loss, is ongoing hard work and not everyone can be a Mark, Julie, Gertrude or Janice.

Thus, although one may well assume that the more radical changes required to precipitate faster weight loss are less likely to be sustainable than more moderate and gradual changes, we must recognise that the effort to keep a given amount of weight off is the same irrespective of whether this weight was lost fast or slow.

AMS
Edmonton, AB