Thursday, January 31, 2013

Obesity Myth #1: The 3,500 Calorie Rule

Yesterday, the New England Journal of Medicine published a paper that addresses common myths, presumptions, and facts about obesity.

As the authors note in their introduction,

“Passionate interests, the human tendency to seek explanations for observed phenomena, and everyday experience appear to contribute to strong convictions about obesity, despite the absence of supporting data. When the public, mass media, government agencies, and even academic scientists espouse unsupported beliefs, the result may be ineffective policy, unhelpful or unsafe clinical and public health recommendations, and an unproductive allocation of resources.”

In this paper, the authors address seven myths, six presumptions and nine facts, which I hope to address individually in upcoming posts.

The first myth addressed in the paper is the common misconception that a continuous daily excess of a few calories per day will result in continuous weight gain.

This myth (also referred to as the 3,500 Calorie Rule) is often presented in a way that numerically adds up the number of excess calories you may be eating per day (say 100) and translates this into weight gain by simply equating 3,500 extra calories to one pound weight gain.

Thus, even academic publications often suggest that a 100 extra calories per day over a year (say about 350 days) would result in 35,000 extra calories or a ten pound weight gain.

You will also often find the converse, where simply burning an extra 100 calories a day is equated to losing 10 lbs.

This, as explained in the paper is a myth because such simplistic calculations do not take into account the physiological mechanisms that result in compensatory energy conservation or expenditure, thereby limiting changes in body weight.

Thus, although a pound of body fat may well represent about 3,500 calories (which it roughly does), an extra pound of body fat is not simply the numerical result of ingesting an extra 100 calories per day for 35 days.

Nor does a daily caloric deficit of 500 calories result in a weight loss of one pound a week, week after week after week, till you finally disappear.

As I have previously explained, significant and ongoing weight gain or weight loss actually requires a substantially greater level of daily caloric excess or restriction that may have to incrementally increase over time to sustain continued gain or loss.

It is therefore safe to ignore statements that are commonly found both in academic publications and in popular media presenting simplistic statements like, “an extra potato chip a day over 20 years can lead to a 50 lb weight gain or an extra can of pop a day can lead to a 20 lb weight gain in one year”.

In reality, ingesting 3,500 extra calories does not simply translate into an extra pound of body fat – nor does burning 3.500 extra calories result in a pound of weight loss.

Or, as I say in my talks, “This is not physics, this is physiology!”

For a detailed discussion of how many calories it actually takes to lose or gain weight click here.

AMS
Edmonton, AB

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Wednesday, January 30, 2013

Even a Modest Lack of Sleep Can Adversely Affect Metabolism

Kevin is a healthy 24 year old student with a BMI of 25, who usually sleeps almost 8 hrs (7:45 to be precise). He is usually fast asleep within 20 mins of lying down and has good quality sleep.

Having always had some interest in research, Kevin (together with 18 other healthy young male students) volunteers to take part in a study on sleep restriction at the University of Surrey, UK, conducted by Denise Robertson and colleagues, the results of which are now published in METABOLISM.

Before beginning the study, the researchers measured Kevin’s body composition (he had 16% body fat), his blood pressure (normal), glucose and insulin levels (normal), adiponectin, leptin and even performed a euglycemic insulin clamp to measure his insulin sensitivity.

As a result of randomization, Kevin ended up in the sleep restriction group and now had to set his daily alarm clock for 1.5 hours before his normal waking time for the next three weeks. He was also told not to nap during the day. Close activity monitoring ensured that he did not cheat on the protocol.

During the first two weeks of sleeping less, Kevin’s body weight actually decreased by about 4 lbs, only to increase slightly above baseline at the end of the study. Similarly, he became more insulin resistant after one week of sleep deprivation, but this returned to normal at the end of three weeks .

Although not much happened to Kevin’s leptin levels during the first two weeks, they fell sharply in week three and were significantly lower than at baseline by the end of the study. (Not much happened with Kevin’s adiponectin levels.)

While Kevin and his colleagues in the sleep deprivation group were experiencing these hormonal changes, not much was happening to the students randomizes to the habitual sleep control group.

As the authors note, the metabolic response to mild sleep deprivation appears to be variable over time with some early changes that may not be sustained over time.

However, they also note that effects of lowered levels of leptin (seen in the third weed) on hypothalamic centres regulating appetite, could potentially lead to increased food intake and weight gain.

This, would need to be looked at in studies with longer duration. Also, what happened to young healthy Kevin, may not be typical for older subjects, women, or those with excess weight or diabetes.

Nevertheless, the study does show that even short term mild sleep deprivation can affect metabolism, even in healthy young men, possibly in a direction that would be conducive to long-term weight gain.

Hopefully, Kevin has by now caught up on his sleep and is not out partying too hard with his buddies.

AMS
Edmonton, AB

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Tuesday, January 29, 2013

Is Yo-Yo Dieting Harmful to Your Metabolism?

Yesterday, I introduced you to Marilyn* and Catherine* – both 58 years old with class 1 obesity.

Marilyn has struggled with her weigh most of her life and has an extensive history of weight cycling; Catherine had never dieted before.

Both participated in a 12 month study of diet and exercise and lost almost the same amount of weight (12% vs. 10%) and had similar improvements in metabolic parameters.

Interestingly, however, prior to beginning the study, there were some small but significant differences between Marilyn and Catherine.

Thus, not only did Marilyn have a slightly higher BMI (33 vs. 30), she also had more body fat (48.8 vs. 46.8%) and a substantially greater waist circumference (99.8 vs. 92.6 cm).

Although their blood pressure levels were identical, Marilyn had slightly higher insulin and leptin levels and was more insulin resistant (as measured by HOMA-IR).

Interestingly, these differences were not explained by differences in caloric intake, calories from fat, cardiorespiratory fitness (VO2max) or daily steps – all of which were virtually identical between the two women.

Thus, although the weight loss response was similar, it may be worth noting that Marilyn, with her history of weight cycling, despite similar caloric intake and physical activity levels, had a slightly less favourable metabolic profile.

Whether or not this difference can be attributed to her history of weight cycling, however, is not clear, as associations do not prove causality.

As the authors note,

“…several analyses where unintentional and intentional weight loss has been clearly distinguished have failed to show an independent association between weight cycling and risk of morbidity or mortality. Moreover, the risk of future weight gain previously associated with weight cycling was recently shown to be greater among women who employ unhealthy weight control strategies rather than ones generally encouraged in most structured behavior change programs .”

Thus, it may not be an issue of whether or not you have weight cycled that matters but rather the methods employed to do so.

These findings are important given the common narrative that weight cycling may be detrimental to physical health (obviously, this study (not any studies that I am aware of) address the potential negative impact of weight cycling on mental health, including self-esteem and body-image).

Would I advise either Marilyn or Catherine to lose weight if I saw them in my office?

Both appear rather healthy (EOSS 0/1) and I would see no urgency in recommending weight loss to either of them. Nevertheless, both Marilyn and Catherine could probably benefit from improving their cardiorespiratory fitness and perhaps increasing their daily steps (both of which happened during the course of the intervention).

Thus, in summary, I concur with the authors that:

“..a history of weight cycling does not impede successful participation in lifestyle interventions or alter the benefits of diet and/or exercise on anthropometric and metabolic outcomes in women. Thus, a history of unsuccessful weight loss should not dissuade an individual from future attempts at weight loss or diminish the role of a healthy diet and regular physical activity in successful weight management.”

As for the risks of weight cycling – I guess, at least metabolically speaking, it may well harbour less risk than we previously thought – although the psychological impact of losing and regaining weight may be something that will require further study.

I’d certainly appreciate hearing from my readers regarding their experiences and thoughts on yo-yo dieting.

AMS
Edmonton, AB

*The characteristics of Marilyn and Catherine are based on the average characteristics of the non-cylcer and severe-cycler participants in this study.

ResearchBlogging.orgMason C, Foster-Schubert KE, Imayama I, Xiao L, Kong A, Campbell KL, Duggan CR, Wang CY, Alfano CM, Ulrich CM, Blackburn GL, & McTiernan A (2013). History of weight cycling does not impede future weight loss or metabolic improvements in postmenopausal women. Metabolism: clinical and experimental, 62 (1), 127-36 PMID: 22898251

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Monday, January 28, 2013

Yo-Yo Dieters Can Lose As Much Weight As Those Who Don’t

This is the story of Marilyn and Catherine.

Marilyn* is 58 years old with a BMI of 33 and has struggled with her weight for most of her life. Not counting pregnancies, Marilyn, has been losing and regaining weight since her early twenties. Although she is usually up and down five to ten pounds as she tries one diet or commercial program after the other, she did indeed lose a very significant amount of weight (well over 20 lbs) on at least three occasions (only to put them back on again).

Catherine* is also 58 years old, is slightly lighter than Marilyn with a BMI of 30, and has never dieted or lost weight before in her life.

Both Marilyn and Catherine (together with 437 other post-menopausal women) decided to take part in a weight-loss study led by Canadian Obesity Network Summer Bootcamper Caitlin Mason, now working with colleagues at the Fred Hutchinson Cancer Research Centre in Seattle, WA.

The participants in the study were randomized to one of four groups (diet, exercise, diet + exercise, or control).

Oddly enough Marilyn and Catherine both end up in the diet + exercise group, and even more interestingly, both women ended up losing almost exactly the same amount of weight.

In fact, Marilyn (the weight cycler) lost 12%, slightly more that the 10% lost by Catherine (the non-cycler).

This was pretty much the result in every group. Irrespective of wether or not the participants had a history of weight cycling or not, the weight loss in controls (0% vs. 0%), diet only (-8.4% vs. -9.1%), or exercise only (-2.4 vs. -2.4%) were almost exactly the same.

In addition, there were no differences between Marilyn and Catherine in their improvements in blood pressure, glucose control and other metabolic variables, showing that a previous history of weight cycling did not diminish the benefits of weight loss.

Thus, the study clearly shows that post-menopausal women with a history of dieting are as capable of losing weight (with the same health benefits) as women, who do not have a history of weight cycling.

So, if weight cycling does not make it harder to lose weight – why worry about a yo-yo dieting?

As I am sure my readers will hasten to point out, there are many other reasons why weight cycling is not a good idea.

Some of these reasons may become clearer tomorrow, when we take a closer look at Marilyn’s and Catherine’s health before they entered this study – so stay tuned.

AMS
Kelwona, BC

*The characteristics of Marilyn and Catherine are based on the average characteristics of the non-cylcer and severe-cycler participants in this study.

ResearchBlogging.orgMason C, Foster-Schubert KE, Imayama I, Xiao L, Kong A, Campbell KL, Duggan CR, Wang CY, Alfano CM, Ulrich CM, Blackburn GL, & McTiernan A (2013). History of weight cycling does not impede future weight loss or metabolic improvements in postmenopausal women. Metabolism: clinical and experimental, 62 (1), 127-36 PMID: 22898251

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Sunday, January 27, 2013

Weekend Roundup: January 25, 2013

As not everyone may have a chance during the week to read every post, here’s a roundup of last week’s posts:

Have a great Sunday! (or what is left of it)

AMS
Edmonton, AB

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In The News

Diabetics in most need of bariatric surgery, university study finds

Oct. 18, 2013 – Ottawa Citizen: "Encouraging more men to consider bariatric surgery is also important, since it's the best treatment and can stop diabetic patients from needing insulin, said Dr. Arya Sharma, chair in obesity research and management at the University of Alberta." Read article

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