Lyle McDonald Interview Part 4 (Why diets fail and obesity)

Posted: October 8, 2008 in Interviews


STEVE: In part 3 of this interview, we talked a lot about carbohydrates. Sticking with diet and nutrition, why, in Lyle McDonald’s mind, do diets generally not work? People seem to do fine for a certain period of time but the weight loss doesn’t ‘stick’ for many. You often hear the blame being placed on set point theory, fad diets, voodoo curses, etc. Personally I like to think it has more to do with the psychology of it all more than anything. It’s most definitely a multifaceted matter, but I’m sure our readers would love to hear your thoughts on the topic.


LYLE:  I think there are a lot of reasons that diets fail and I generally group them into physiological factors (hunger, lethargy) and psychological.  I suspect (but have little but empirical data to support this) that individuals at different levels of the body fat spectrum are relatively more or less impacted by each.  So in lean athletes, usually food control isn’t much of a problem.  But the body is often fighting back very hard when people get very lean. So the physiological factors (leptin, ghrelin, etc) are contributing relatively more here in my mind.  Of course, that population doesn’t describe the majority of dieters in the first place so I won’t focus on it much here.

At the opposite extreme, when people are fatter, usually the impact of the physiological systems is less important but the psychological factors are far more important.  We live in a world where high calorie, tasty food is available cheaply and easily, people are bombarded absolutely constantly by advertisements and such for high calorie foods.  That alone can drive hunger and consumption even in the absence of true physiological hunger.  Of course, this is what food advertisers explicitly set out to do.

But moving beyond that, what you’re really asking about is why diets per se fail and I agree that a lot of what’s going on is psychological.

Of course, one of the simplest is the fact that behavior change of any type is always hard.  The simple fact is that most people, regardless of what habit you’re discussing, will tend to revert to older (and hence more, well-entrenched) habits because it’s usually easier and less stressful.  Smoking, drinking, exercise and eating habits are all difficult to change; this suggests to me that there is some aspect of human behavior that generally makes changing habits difficult.  Of course, the corollary of this is that the longer people stick with any new habit, the more entrenched it becomes and the more likely it is to become the new constant habit.  The problem, I think, comes in when folks are expecting years of one habit to magically disappear overnight, or in a few weeks.

Which brings me in sort of a roundabout way to one of the behaviors that I think can be the most destructive when it comes to dieting and that’s expecting 100% perfection.  There is an attitude among dieters that when they ‘go on a diet’, they are either on the diet or they aren’t. They take this extreme attitude that everything must be perfect and that any deviance from the diet means complete failure.  This almost invariably leads to a spiral of self-destructive behavior, usually involving food.  So you have someone who is moving along with their diet a few days in and the inevitable craving occurs.  So they eat that cookie (let’s say it has 50 calories).  The guilt sets in, the diet is clearly blown, therefore they might as well just blow their diet, eat the entire bag of cookies, maybe go get some more junk food, etc.  It’s exceedingly prevalent and, when you look at it objectively, pretty absurd.

Let’s say that someone is on a nice moderate deficit diet eating 500 calories per day less.  They have that 50 calorie cookie that isn’t ‘on their diet’.  They still have a 450 calorie deficit; they haven’t ruined their diet or destroyed the day or anything like that.  Well, not until they eat the remaining bag to the tune of 800 calories (or more).  What could have been dismissed as a pretty irrelevant slip up is invariably made into a much bigger deal by the psychological guilt.

Researchers have actually looked at this type of behavior, which is often referred to as ‘rigid dieting’; they are describing dietary approaches that are extremely rigid with absolutely no room for flexibility.  In contrast, there is also the concept of flexible dieting.   Whereas rigid dieters are either on their diet or off their diet, flexible dieters allow for more flexibility in their eating patterns.  Interestingly, flexible dieters often weigh less and are more likely to stick with their eating habits in the long-term.  I actually thought this concept was important enough that I wrote an entire book about it, looking not only at the rigid/flexible dieting mentality but other issues as well.

In that book, after a rather lengthy discussion of both the physiological and behavioral things that can derail diets, I discuss three concepts that I think are valuable to help avoid the above issues: free meals, refeeds and full diet breaks.  In the context of your original question, I’m only going to detail the first.

Free meals are exactly that, meals planned into a weight loss diet where the dieter can eat relatively freely. Now, this doesn’t mean going and trying to bankrupt the buffet but rather a meal that doesn’t conform to the restrictive nature of the diet.  I find that, psychologically, knowing that one or two normal meals can be eaten per week goes a long way towards helping people avoid not only the seeming deprivation nature of the diet but also helping to avoid the behavior I described above.  As well, it helps people realize that a single meal can’t destroy a diet, even a couple of meals per week that are not ‘on the diet’ doesn’t really do much damage (unless the person seriously loses control). I mean, look at it this way; say someone is eating a standard 4 meals per day on their diet.  That’s 28 meals per week.  If two meals don’t conform to the diet, then that’s less than 10% of the total meals. That doesn’t hurt anything.

Of course, the danger can be that one free meal becomes another free meal and the diet stops being a diet.  A balance has to be found which is why I give fairly specific recommendations of how often free meals can or should be eaten, along with some rules to try to keep them from becoming out of control gorge-fests.

And, frankly, a lot of this comes down to the issue of control.  I find that, when people feel that they have broken their diet ‘accidentally’ (e.g. they got that craving and had a little bit), that tends to lead to the kind of destructive spiral I described above.  In contrast, when the dieter feels that the break from their diet is in their control and, in fact, a planned part of their diet, the likelihood of this happening is much less.

An interesting study several years back really brought this home for me.  In that study, the researchers wanted to try to study what causes diets to fail in the long-run, based on the assumption that dieters fall off the wagon when they break their diet.  So they put a bunch of folks on the diet and then told them to take two weeks off to see what would happen.  In contrast to what they expected, the dieters didn’t all regain the weight and start eating like crazy.  They didn’t actually gain much weight at all and were able to return to their diet after the break.  As I recall, the researchers didn’t have a good idea of what caused this to occur but I really think it’s about control: the dieters didn’t see the two weeks ‘off’ the diet as out of their control.  They didn’t feel the psychological impact of having ‘broken their diet’.  Rather, they interpreted it as simply being a planned part of the program, they dieted, they took two weeks off, they went back to their diet.

I integrated that concept into the Guide to Flexible Dieting as something I called a full diet break; this is a period in-between phases of active dieting where the dieter should simply eat ‘normally’ and at maintenance.  Frankly, at least one reason that diets fail in my opinion is that people diet for too long and it just gets to be a psychological grind.  People who are extremely overweight may be looking at a year or more of dieting to get to a ‘normal’ weight (whatever that means exactly).  Expecting them to do it in one long stretch is unrealistic in my mind.  Rather, breaking the dieting up into more manageable phases makes more sense.  Diet 6-8 weeks (or however long), while incorporating free meals mind you, then take a break where weight is stabilized, the current eating habits are further entrenched (the diet break shouldn’t be a period where the person just eats uncontrollably) and then do another dieting period to bring weight down further.  Stabilize for a couple of weeks, etc.

Of course, the diet break can also be used for things like vacations or holidays, common trouble periods where people’s best dietary habits become derailed.  By planning the breaks (that are now under the person’s control) during those times, I think getting back on the diet afterwards is more likely. At least some of the habits developed during the actual diet can be kept up during the holiday but the person doesn’t have to be a social pariah. After the break, the diet can be resumed.

In any case, I could probably go on and on about this.  Frankly, I think that figuring out some of the psychological blocks behind long-term behavior change is a lot more important than looking at specific diets.  Nutritional research has been trying to find the optimum diet for weight loss for thirty years.  Not only doesn’t any single diet exist that is right for everyone but I frankly think that the research is a bit misguided.  Determining what diet is best isn’t usually the problem; figuring out how to get people to actually stick with the change in diet (or exercise) in the long-term is.  That’s where the physiologists, dietitians and psychologists need to get together to look at the behavioral aspects of all of this.


STEVE:  I couldn’t agree more with that last sentence… the entire response actually.  In my opinion people need to spend a lot more time thinking about what they’re thinking about. Sounds silly to some I’m sure, but the fact in the matter is most of us are on autopilot.  We are in reaction mode based on our neurological conditioning that has been established and ingrained over a lifetime.  Consciously we’re able to gain some control and generate progress acutely.  For most though, until we’re able to find ways to recondition or reprogram our habitual thought patterns, success is not going to be permanent.

The first step, again in my opinion, is simply spending time listening; listen to the things that internal voice says day in and out.  Spend time sifting through your mind and indentifying some of these mental constructs that set you up for failure.  We can’t fix what we haven’t identified.  The one you speak of here regarding the rigid dieter is rampant among today’s dieters.

It’s a complex topic, yet, I’ve seen drastic improvements with rather simple solutions.  So simple in fact that people overlook them.  

I’ve read A Guide to Flexible Dieting a few times since much of what you discuss in that book correlates to the common client we come across and I can’t recommend the book highly enough to our readers.

Now for a theoretical question… where do you see obesity heading in the future?  Do you see drugs playing the primary role in the solution?  Do you think we are anywhere near close to fixing the problem?  Once there’s a solution, will it fix people already struggling with obesity or will it only prevent it from happening in pre-obese individuals?   Obviously you don’t have definitive answers so we’re simply looking for your thoughts on the topic.


LYLE:  I don’t know if drugs will play the primary role but I think that they will have to play an accessory role.  It’s becoming abundantly clear that the human body has a number of complex, overlapping systems which regulate hunger, appetite and bodyweight.  This includes the old standbys of leptin, ghrelin, insulin, peptide YY and CCK along with newly found systems such as the endocannabanoid system (drugs to target this are currently under development).  It’s becoming increasingly clear that attacking any single system is probably destined to fail, the body is simply too good at recruiting other pathways that compensate.

Here’s an example: it’s well known that most weight loss drugs cause a reasonably small weight loss (around 10% weight or so) and then stop working.  It’s usually been assumed that the body stops responding to the drug or develops tolerance but some data (in animals so far) suggests otherwise.  What people forget is that as people lose weight, hormones such as leptin alter in such a way that the body starts compensating for the weight loss.  So while the initial drug was working just fine to begin with, by the time the body adapts (via a lowering of leptin for example), the drug appears to have ‘stopped working’.  Of course that’s not true, it’s working just fine, the body has simply adapted.  In one interesting study (again, in rats), they compared sibutramine (a currently in use weight loss drug) to leptin by itself or sibutramine with leptin. While both the sibutramine and leptin only groups hit an early plateau, the sibutramine plus leptin group kept losing weight.  Why?  Because by replacing leptin, the rats bodies were kept from compensating to the weight loss caused by the sibutramine alone.

Related to this, a few human studies have found that replacing leptin to pre-diet levels (by injecting dieters after they had lost some weight) normalized metabolic rate, blunted hunger, and caused further fat loss.  Bascially, while leptin has been an utter failure at causing weight loss in obese individuals, it appears to have its major effect in keeping diets working by preventing the body from adapting.  I’d note that this is essentially what I try to accomplish in my books by including high-carb/high-calorie refeeds and diet breaks; I’m trying to raise leptin levels to limit the body’s adaptation to the diet.

In any case, some type of polypharmacological approach targeting a variety of pathways is far more likely to be effective than any singular treatment.  Additionally, I expect that as more research determines all of the potential places where eating behavior *might* become disordered (e.g. the reason why one person becomes obese may be different than the reasons another becomes obese), obesity treatment will become individualized either with respect to diet, exercise, drugs or the combination.  Research has already emerged (as I mentioned in a response to a previous question) showing that insulin resistant individuals respond differently to certain diets than insulin sensitive individuals.  Determining what specifically is going on in any one individual should allow for more tailored approaches to obesity treatment.

As far as prevention, I could see this being another fertile field as well (and some researchers think that preventing obesity is going to do more good than trying to correct it after the fact anyhow), identify individuals who have predisposing factors for the development of obesity, whether it’s a slightly low metabolic rate for their weight or what have you, and correct the defects before a problem presents itself.

Unfortunately, I think a lot of this being practically applied is still quite some time off.  Until that time, the stock standard approach of finding livable long-term changes to eating and activity patterns that can and will be maintained in the long-term is going to be the key.

  1. maleficent1964 says:

    really good conversation above… and applicable to a lot of people…

  2. […] « Lyle McDonald Interview Part 4 (Why diets fail and obesity) […]

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