Metabolically Active Fat
Recent evidence suggests that brown adipose tissue (BAT) exists into adult hood and can, when present account for as much as 20% of daily resting energy expenditure. While the exact contribution of BAT (or lack thereof) to obesity remains to be determined, the presence and inducibility of BAT by cold exposure is inversely related to BMI, appears higher in women, and diminishes with aging. Given the role of cold exposure in the expression of BAT, it can be speculated that an increase in ambient temperature may promote weight gain by significantly reducing BAT and, thus, metabolic rate in some individuals. In rodents, increased production of neuropeptide Y in the hypothalamus can not only increase food intake but also reduce energy expenditure via a reduction in non‐shivering thermogenesis in BAT and facilitate triglyceride deposition through increased insulin levels.
A wide range of medications can affect metabolic rate. Notably, the use of beta‐blockers has been shown to significantly reduce thermogenesis, resulting in clinically relevant weight gain 34. Metabolic rates can also be reduced by the discontinuation of drugs that promote thermogenesis such as beta‐adrenergic agents, stimulants (including performance‐enhancing and illicit drugs like crack/cocaine), coffee or nicotine, resulting in weight gain.\
Finally, weight loss can markedly reduce energy requirements with a 5–10% reduction in body weight reducing resting metabolic rate by as much as 20% in some individuals, thereby substantially increasing the susceptibility to weight regain in the post‐obese state.
Commentary: In summary, any of the many factors that can reduce metabolic rate, can result in weight gain even with no change in energy intake or energy expenditure. In a clinical setting, this would apply to the patient, who tells you that they have not changed their food intake or their activity levels and, yet, have gained weight. Rather than simply discarding this information from a patient as being untrue or “delusional”, clinicians should give careful consideration to the factor that there very well may be factors that have led to a significant reduction in metabolic requirements.
I was recently, once again asked about my opinion on weight-loss challenges. So here is a repost of an article I wrote back in 2008 on this topic – apparently, it is still as relevant today, as it was almost a decade ago.
There appears to be a rather widespread notion out there that introducing a bit of competition into the affair may spurn people on to try and lose those “extra” pounds.
In fact, a quick google search on the term “weight-loss challenge” reveals an amazing array of challenges from voyeuristic and sadistic TV shows like the “Biggest Loser” to well-meant workplace wellness initiatives or fund raisers. I am sorry to admit that I recently even became aware of a weight-loss challenge within my own hospital – well intended, but useless in the fight against obesity.
So what’s wrong with this idea? Isn’t competition a great motivator?
Sure it is – and people will do anything to win a competition – including crazy stuff like starve themselves, exercise till they drop, or even (God forbid) pop diet pills, diuretics or laxatives just to win.
All of this is in direct contradiction to a fundamental principle of obesity management: you do not do things to lose weight that you are unlikely to continue doing to keep the weight off.
Most people seem to think that if only they could lose some weight, they will somehow be able maintain that lower body weight in the long-term with less effort.
The reality unfortunately is (and most dieters have experienced this over and over again) that no matter what diet or exercise routine you chose, no matter how slow or fast you lose the weight, no matter how long you keep the weight off – the minute you relax your efforts, the weight simply comes back.
As I have blogged before: obesity is a chronic disease for which we have no cure – only treatments! When you stop the treatment the weight (and any related problem) simply comes back.
By now you will already have figured out the problem with these challenges – unless you are very modest and reasonable about your weight-loss target and are carefully making changes that you can reasonably sustain forever, you are simply setting yourself up for failure.
If you are indeed modest and reasonable – you’ve already lost the competition to all the crazy folks who’ll do anything just to win.
My advise to anyone with a weight problem – the next time you see an invitation to a weight-loss challenge – simply ignore it!
If you really think you will benefit from obesity treatment – seek help from a trained and accredited health professional with experience in weight management – let’s put an end to weight cycling!
Obesity medicine, which I define as the medical care of someone living with obesity, should approach patients holistically with the aim of improving their overall health and well-being. Advice to lose weight may or may not be part of obesity management – much can be gained for someone living with obesity by promoting their health behaviours, getting them to feel better about themselves, improving their mental health, and helping them better managing their health issues. Much of this can be achieved with no or very little weight loss.
Thus, we must consider the question of when weight loss would specifically need to be part of the treatment objectives.
In my own practice, I approach this problem by considering the following three questions:
- Is this a problem unrelated to abnormal or excess body weight?
- Is this a problem aggravated by abnormal or excess body weight?
- Is this a problem caused by abnormal or excess body weight?
From what I hear from my patients, the most common mistakes in medical practice fall into the first group – trying to address unrelated issues with weight loss recommendations. There are endless stories of patients going to see their health provider with problems clearly unrelated to their body fat (e.g. a broken arm, a sore throat, the flu, depression, migraines, etc.), who simply get told to lose weight. Indeed, there is evidence to suggest that patients with obesity are less likely to undergo diagnostic testing, most likely based on the assumption that their problems are simply related to their excess weight. This is not only where grave medical errors can be made (late or misdiagnosis), but also where the advice to lose weight is clearly wrong. If the presenting problem has nothing to do with excess weight, then no amount of weight loss will fix it.
The second category deals with issues that are not causally related to abnormal or excess body fat but where the underlying problem either causes more symptoms or is more difficult to treat because of the patient’s size or fat distribution. There are countless medical problems that fall into this category. For e.g. a heart or respiratory problem entirely unrelated to excess weight (e.g. a valvular defect or asthma) can become worse, cause more symptoms, or be much more difficult to treat simply because of the patient’s size. This group also includes issues like neck or joint pain from a trauma (e.g. a motor vehicle or skiing accident), reflux disease (e.g. from a hiatal hernia), urinary incontinence (from multiple child births), etc., etc., etc. – the list is long. Here, although obesity has nothing to do with the underlying problem, weight loss may alleviate the symptoms or at least make them more manageable (they are however unlikely to be fully resolved). These patients present with what may be described as a relative or “secondary” indication for weight loss. Of course, if there are viable treatments options for the primary problem, then this is where the emphasis should be. Weight loss can best be considered as “second-line” treatment. It would be completely unethical to withhold effective treatment for the underlying problem just because of the patient’s size (as in, “no treatment for you until you lose X lbs!”)
Finally, we have the third category of health issues that are directly causally linked to the excess weight – in most cases, the problem did not exist prior to weight gain and losing weight is often likely to completely resolve the problem (unless the patient has already sustained irreversible organ damage). This group of health issues not only includes the vast majority of cases of type 2 diabetes, hypertension, obstructive sleep apnea, fatty liver disease, infertility, etc. but also all of the functional limitations that people may experience simply because of their excess body fat. This is the only category of patients who would be deemed to have a “primary” indication for weight loss. Losing the weight literally solves their problem. Indeed, trying to manage the problem without weight loss is nothing less than “palliative” care. This is not to say that weight loss will always guarantee success even if the underlying problem is directly related to excess weight. For e.g. although there is ample evidence that excess weight is a prime risk factor for gall bladder disease, (rapid) weight loss may actually promote formation of gall stones. Similarly, although intertrigo (skin fold infections) can occur as a direct consequence of excess weight (e.g. chaffing), losing weight may actually make the problem worse by deepening the skin folds. Thus, even in this category, one needs to carefully consider risk-benefit ratios.
Of course, any recommendation to lose weight must take into account the complex nature of obesity in the first place and the fact that long-term weight-loss maintenance will require an approach (behavioural, medical, or even surgical) that takes into account the chronic relapsing nature of this disorder. Simply telling people with obesity to “eat less and move more” is about as medically sound and effective, as simply telling people with depression to “cheer up”.
Both, to avoid grave medical errors and to not insult their patients, I strongly recommend that medical practitioners first approach all their patients with obesity based on the assumption (that their presenting health issues are unrelated to their excess weight) before considering possibilities two (unrelated but aggravated) and three (causal). Advise to lose weight has no role in situation 1, can be considered in situation 2, and is clearly the best course of action for situation 3.
In my experience, patients presenting with obesity tend to fall into three categories, each of which requires a distinct management approach.
They are 1) Active Gainers, 2) Weight Stable, and 3) Post-Weight Loss.
Active Gainers are patients currently at their lifetime maximum and continuing to gain significant amounts of weight – i.e. more than the usual 0.5 to 1 lb/year. Patients in this category require immediate attention – if nothing happens, their weight will most likely just continue to increase. The good news is that in almost every patient in this category, there is an identifiable reason for the ongoing weight gain – this can be psychosocial (e.g. depression, binge-eating disorder, etc.), due to a medical comorbidity (arthritis, chronic pain, etc.) or medications (e.g. atypical antipsychotics, hypoglycemic agents, etc.). From a management perspective, the sooner we identify and address the underlying problem, the sooner we can slow or even halt the rate of weight gain – in this patient – gaining less weight than before is the first sign of success. There is really no point trying to embark on losing weight as long as the underlying problem driving the weight gain has not been addressed, as this is likely to make sustained weight loss even more unlikely that it already is..
Weight Stable patients are those that present with excess weight but are relatively weight stable. Even though they may be at their lifetime maximum, they have been pretty much the same weight (perhaps a few lbs up or down but nothing drastic) for several years (sometimes even decades). By definition, a patient who is weight stable is in caloric balance, and thus, by definition is not eating too much. In fact, these patients are eating the exact number of calories needed to sustain their bodies, which is why they are weight stable. (Remember, even if you are weight-stable eating 4000 Cal a day, you are technically not “overeating”.) These patients of course have experienced significant weight gain in the past (historical weight gain), but whatever it was that caused them to gain weight is no longer an active problem (e.g. pregnancy, past depression, etc) – and therefore, probably doesn’t need to addressed (although, I always find it of interest to find out what caused the weight gain in the first place). With these patients, we can determine whether or not their weight is affecting their health, and if it is, we can jump right into discussing treatment options (behavioural, medical and/or surgical).
The third group of patients, Post-Weight Loss, are those who are not at their lifetime maximum, or in other words, have already lost weight (by whatever means). These patients generally present either because they want to lose even more weight (Doctor, my diet has stopped working! = “weight-loss plateau“), or are experiencing weight regain (Active Regainers). In case of the patients experiencing a “weight-loss plateau”, one needs to determine if there is in fact any medical indication for further weight loss – many of these patients may already be at their “Best Weight”. If there is indeed a medical indication for further weight loss, it generally means adding therapeutic options that may include anti-obesity medications and/or surgery. (In my experience, patients who have been maintaining a significant amount of weight loss on their own, generally leave little room for further behavioural intervention). On the other hand, there are the post-weight loss patients who are actively regaining weight. These tend to fall into two groups – the first one are those, who have lost a significant amount of weight with a strategy that is in fact unsustainable (e.g. a very low-calorie diet, an excessive exercise program, or whatever else desperate patients will try just to drop their weight). As the strategy they were on is not one that they can sustain (for good reasons), some weight regain is inevitable and the best we can do is to offer a weight management strategy that is sustainable in the long run (and may include medication or surgery) . The other group of Active Regainers, are those that were on a more-or-less sustainable management plan (behavioural, medical or surgical) and have for some reason “fallen off”. Here one needs to determine what exactly they have stopped doing (e.g. no longer keeping their food journal, stopped their anti-obesity medications, etc.) or what additional weight-gain promoting change has occurred that has thrown them off (again, reasons can be psychosocial or medical). Here one needs to determine if the patient can in fact go back to doing what was “working”, which may require addressing the new problem that has arisen or add additional therapeutic options (e.g. medications or surgery).
Thus, as each type of patient needs a somewhat different assessment and management strategy, I find this approach to thinking about each patient most helpful.
Comments are very much appreciated.
Regular readers will be well aware of the increasing data supporting the importance of adequate restorative sleep on metabolism and weight management.
Now, a study by Wang Xuewen and colleagues, published in SLEEP, shows just how detrimental sleep deprivation can be during a weight-loss diet.
Their study included thirty-six 35-55 years oldadults with overweight or obesity, who were randomized to an 8-week caloric restriction (CR) regimen alone (n=15) or combined with sleep restriction (CR+SR) (n=21). All participants were instructed to restrict daily calorie intake to 95% of their measured resting metabolic rate. Participants in the CR+SR group were also instructed to reduce time in bed on 5 nights and to sleep ad libitum on the other 2 nights each week.
The CR+SR group reduced sleep by about 60 minutes per day during sleep restriction days, and increased sleep by 60 minutes per day during ad libitum sleep days, resulting in a sleep reduction of about 170 minutes per week.Although both groups lost a similar amount of weight during the study ~3 Kg). However, the proportion of total mass lost as fat was significantly greater in the CR group (80% vs. 16%).
In line with this substantial difference in fat reduction, resting respiratory quotient was significantly reduced only in the CR group.
Importantly, these effects of sleep deprivation on fat loss were observed despite the fact that subjects were allowed to sleep as much as they wanted on the non-restricted days. This suggests that the negative effects of sleep deprivation during weight loss are not made up by “make-up” sleep.
Although overall, the amount of weight lost in this study is modest, it clearly fits with the notion that adequate sleep (in this case, during weight loss), can be an important part of weight management.
Clearly, the role of sleep in energy homeostasis will remain an interesting field of research, as we continue learning more about how sleep (or rather lack of it) affects metabolism.