Arya M. Sharma, MD

Diurnal changes in hormones and metabolism are well known and how these can be influenced by timing and sequencing of external stimuli (e.g. eating, exercise, sleep, etc.) has always been of considerable interest.

A study by Sigal Sofer and colleagues from the Hebrew University of Jerusalem, Israel, published in OBESITY, suggests that eating most of your carbs at dinner may have beneficial effects on hormonal patterns, metabolism, and lead to more weight loss than eating a similarly calorie-restricted diet with carbs spread out throughout the day.

The rationale for the study as stated by the researchers is that:

“…consumption of carbohydrates mostly in the evening would modify the typical diurnal pattern of leptin secretion as observed in Muslim populations during Ramadan. The experimental diet induced a single daily insulin secretion in the evening, thus it was predicted that the diet would lead to higher relative concentrations of leptin starting 6–8 h later i.e., in the morning and throughout the day. This may lead to enhanced satiety during daylight hours and improve dietary adherence.”

In addition,

“Studies have shown that there is a negative correlation between insulin and adiponectin levels. Since the experimental diet used in this study reduces insulin secretion during the day, it was also hypothesized that adiponectin concentrations would increase throughout the day improving insulin resistance, diminishing symptoms of the metabolic syndrome and lowering inflammatory markers.”

A total of 78 male subjects (policemen) with a BMI greater than 30 were randomized to 6 months of 1,300–1,500 kcal/day diets, with either the carbs served mostly at dinner (test) or throughout the day (control).

Subjects eating their carbs in the evenings lost more weight (11.6 vs. 9.06 kg) and had lower hunger scores as well as greater improvements in fasting glucose, average daily insulin concentrations, and insulin-resistance.

There were also greater improvements in lipid profiles, CRP, and other relevant markers in the intervention group.

While leptin levels dropped in both groups (not surprising given the weight loss), the leptin decrease was less in the late-carb-eaters than in the control group, and adiponectin levels increased significantly only in the intervention group. The authors suggest that these hormonal changes may perhaps explain the improved metabolic control and lower hunger scores in this group.

However, the authors are also careful to point out that:

“Further research is required to confirm and clarify the mechanisms by which this relatively simple diet approach enhances satiety, leads to better anthropometric outcomes, and achieves improved metabolic response, compared to a more conventional dietary approach.”

They certainly have my attention.

AMS
Edmonton, Alberta

p.s. Registration for the International School on Obesity Research and Management (ISORAM 2012, Lake Louise March 25-30 is now open - click here to register).

Sofer S, Eliraz A, Kaplan S, Voet H, Fink G, Kima T, & Madar Z (2011). Greater weight loss and hormonal changes after 6 months diet with carbohydrates eaten mostly at dinner. Obesity (Silver Spring, Md.), 19 (10), 2006-14 PMID: 21475137

Hundreds of animal studies show that restricting caloric intake (while avoiding malnutrition) can expend the lifespan - often by periods, which translated into humans, would amount to an impressive number of years.

How does this work and can any of these findings be relevant to promote healthy aging in humans?

This is the topic of an article by Miranda Sung and Jason Dyck from the University of Alberta published in Heart Failure Reviews.

In animal models, the effects of caloric restriction on longevity is in part explained by a range of mechanisms that include:

1. Preventing age-associated changes in gene expression,

2. Enhancing innate cardioprotective signaling pathways that increase stress tolerance,

3. Reducing the risk factors for developing CVD,

4. Preventing and/or delaying the onset of age-related chronic diseases, including hypertension, atherosclerosis, type 2 diabetes, and cardiomyopathy

Interestingly, some of these effects can be mimicked by resveratrol, an active ingredient in red wine - one reason why the authors describe resveratrol as a ‘calorie-restriction mimetic’.

With regard to the potential benefits of caloric restriction in humans, the authors point out that:

“Due to the long lifespan of humans, the lack of universally accepted biomarkers of aging, and the difficulty of conducting long-term, randomized calorie restriction studies, there are limited data regarding longevity and dietary restriction in humans. However, epidemiological data appear to support findings in non-human primates discussed above that calorie restriction may have beneficial effects on longevity and health. For example, the inhabitants of Okinawa island in Japan consumed an estimated 15 and 40% fewer calories as compared to mainland Japanese and U.S. residents, respectively, yet Okinawans have the highest life expectancy in Japan and possibly the world and the largest percentage of centenarians in the world.”

Obviously, there could be other reasons for this ‘association’ in the Japanese and such data would be considered far from conclusive.

Thus, despite the evidence from animal studies and some indications that calorie restriction in humans may lead to similar biological effects (at least at the molecular level), it is certainly unclear whether calorie restriction (or reserveratrol) will reduce age-related cardiovascular disease in humans.

I may need a glass of red wine to relax and think about this.

AMS
Toronto, Ontario

Sung MM, & Dyck JR (2011). Age-related cardiovascular disease and the beneficial effects of calorie restriction. Heart failure reviews PMID: 22095297

Glycemic Index (GI) refers to comparable ease with which a given carbohydrate load appears in the circulation - this index varies considerably between various sources of carbohydrate and is a function of the ease with which this carbohydrate is digested into and absorbed (as glucose) into the blood stream.

But how important the GI of foods, especially when meals are not consumed in a highly controlled research setting, in determining glucose profiles remains an area of debate.

In a study, just published in the Journal of Nutrition, we looked at the relationship between the GI of a self-selected breakfast consumed in ‘free-living’ individuals by studying their glycemic response for two hours after breakfast using continuous glucose monitoring.

We studied 57 non diabetic overweight and obese adults with a mean BMI of about 34 and mean waist circumference of 109, who underwent a 75-g oral glucose tolerance test (OGTT) and, on a separate day, wore a continuous glucose-monitoring system (CGMS) for 24 h during which time they recorded all foods consumed.

The protein, fat, and available carbohydrate (avCHO) content and GI of the breakfast meals were calculated from the food records and the incremental areas under the glycemic response curves (iAUC) for 2 h after breakfast (iAUC(breakfast)) were calculated from CGMS data.

The measured variables accounted for almost 60% of the total variation in glycemic response, with the GI explaining by far the greatest proportion of this variation (30%). The response to the OGTT and avCHO explained an addition 11% each with waist circumference explaining a further 3%.

The effects of fat, protein, dietary fiber, age, sex, and BMI were not significant determinants of glycemic response.

Our study thus shows that the GI is a significant and more important determinant of individual glycemic responses elicited by self-selected breakfast meals, than just the intake of carbohydrates.

These findings certainly support the notion that one should perhaps look beyond simply the grams of sugar or carbohydrates in your diet to determine the actual glycemic risk of foods.

AMS
Edmonton, Alberta

Kochan AM, Wolever TM, Chetty VT, Anand SS, Gerstein HC, & Sharma AM (2011). Glycemic Index Predicts Individual Glucose Responses after Self-Selected Breakfasts in Free-Living, Abdominally Obese Adults. The Journal of nutrition PMID: 22090469

This question appears almost a ‘no-brainer’ and many readers will once again put the very fact that I touch on this topic down to ’sports-bashing’ - but, the ‘uncomfortable truth’ for youth sports enthusiasts is that the answer to this question is far less clear than one would perhaps expect.

Given the rather mixed literature on whether or not (organized) youth sports can provide a solution to the obesity problem, Toben Nelson and colleagues from the University of Minnesota, Minneapolis, have taken a careful look at the published literature on this issue - their findings are published in the latest issue of Current Sports Medicine Reports.

While their review of 19 studies on this topic showed that kids participating in sports were indeed more physically active than kids who did not participate, overall they found no clear relationship between participation and weight status. While 12 studies did note some (albeit small) differences in body weight in selected subgroups (but not the entire study population in these studies), the other 7 studies found no differences in body weight at all.

Further analyses of these studies revealed some ’surprising’ findings that may well explain these findings:

Firstly, there were substantial disparities between the overweight and obesity rates between sports: sports with a higher level of obesity included rugby, swimming, judo, and tennis, and sports with lower levels of obesity included gymnastics, handball, horse riding, and dance.

Thus, as the authors note:

“The lack of a clear difference in weight status between participants and nonparticipants observed in some of the studies reviewed may be attributed to the type of sport studied and the specific body type suited for that sport.”

Secondly, although kids participating in sports tend to have more activity than non-participating kids, the overall differences are not as large as one would assume. While in one study, on the days on which kids participated in sports added about 30 mins of moderate to vigorous physical activity to that day, another study that objectively assessed physical activity of youth sport participants in soccer, baseball, and softball, found that fewer than one in four met recommended levels of activity during their sport team practice.

“It is not clear from these studies how much of the sedentary time in sport was spent in these sport-related activities and it is also not clear what extent to which physical activity can be optimized in these settings without sacrificing instruction and skill development.”

Thirdly, it is very possible that participation in youth sports can negatively affect both the quality and quantity of food and drink consumed, potentially resulting in net positive energy balance.

Thus, although one study found that youth involved in sport had better overall nutrient intake than youth not involved in sport, several other studies showed that total caloric intake often exceeded actual expenditure. One study of middle and high school youth found a positive association between sports team participation and frequency of fast food consumption and that sport team participation during middle school predicted greater fast food consumption into the high school years. In other studies, sport participants were more likely than nonparticipants to consume sports drinks and fruit juice and were equally likely to consume soft drinks.

As the authors point out:

“Candy, confectionary, sugar-sweetened beverages (including sport drinks), and ice cream are commonly sold at youth sport events or brought to the event by contestants and parents. Youth sport marketing is a key part of food and beverage marketing strategies, and voluntary industry guidelines may actually encourage food and beverage companies to associate those products with health and fitness activities such as youth sport.”

“Among some sport teams and leagues, the practice of providing snacks and beverages is institutionalized, wherein volunteer parent coordinators develop and assign a snack schedule. The snacks and beverages provided are often packaged convenience food (e.g., sport drinks, soda pop, candy bars, cookies, chips, “fruit” snacks) and, in combination, could total 300 to 500 calories or more.”

This is certainly problematic as,

“Youth, parents and coaches may have little or no awareness of the large number of calories contained in snacks and beverages commonly offered in youth sport settings or the relatively small number of calories children expend during sport.”

The authors also discuss the observations that:

“In addition to direct access to excess calories available in sport settings, participants are subject to time pressures associated with attending sport practices and events. Time pressures may lead to more consumption of fast food and other processed food, which tend to be convenient but less healthy options. Regular family meals are associated with healthful dietary behaviors but may be sacrificed due to sport participation. Parents of youth sport participants report that sport-related time pressures influence meal planning and preparation, interfering with family meals.”

Another issue concerns the almost inevitable discontinuation of sporting activity, which may occur for numerous reasons including personal factors such as lack of enjoyment or motivation, time constraints, pressure to perform, and low achievement orientation and organizational factors such as coaching issues, lack of playing time, and lack of opportunities to participate.

“Regardless of the reason for dropping out of sport, decreasing energy expenditure without replacement with other forms of physical activity and/or decreasing caloric intake can promote energy surplus and weight gain. Childhood eating patterns help establish adult dietary habits, and these findings highlight the importance of promoting good nutrition in conjunction with youth sports.”

Overall, the authors conclude that:

“Given the limited available research, there is not sufficient evidence to conclude that sport participation protects against the development of obesity. Additional research is needed to understand weight status and weight gain among sport participants and to determine whether, and under what conditions, sport can effectively prevent unhealthy weight gain.”

At a minimum:

“Additional discussions among key stakeholders are needed, and interventions to reduce the exposure to the excessive calories and other unhealthy food and beverage options available in youth sport must occur before the promise of obesity prevention in youth sport can be realized.”

As I have discussed before, it appears that both the potential benefits and downsides of sports as a means to tackling obesity have more to do with the impact of sports (and sport settings) on caloric intake than expenditure.

AMS
Edmonton, Alberta
Nelson TF, Stovitz SD, Thomas M, Lavoi NM, Bauer KW, & Neumark-Sztainer D (2011). Do youth sports prevent pediatric obesity? A systematic review and commentary. Current sports medicine reports, 10 (6), 360-70 PMID: 22071397

Today’s post is another excerpt from “Best Weight: A Practical Guide to Office-Based Weight Management“, recently published by the Canadian Obesity Network.

This guide is meant for health professionals dealing with obese clients and is NOT a self-management tool or weight-loss program. However, I assume that even general readers may find some of this material of interest.

EATING PATTERNS

A patient’s eating patterns provide important clues about possible contributors to obesity and will help you design an appropriate treatment plan. Eating behaviour is highly variable. Some behaviours meet the stringent criteria of an eating disorder as defined by DSM-IV criteria (e.g., binge-eating disorder or bulimia). Other abnormal eating behaviours can be considered maladaptive rather than formally diagnosable. These include meal skipping, snack skipping, emotional eating, stress eating, boredom eating and night eating syndrome. Such behaviours are often not accompanied by feelings of guilt or distress.

© Copyright 2010 by Dr. Arya M. Sharma and Dr. Yoni Freedhoff. All rights reserved.

The opinions in this book are those of the authors and do not represent those of the Canadian Obesity Network.

Members of the Canadian Obesity Network can download Best Weight for free.

Best Weight is also available at Amazon and Barnes & Nobles (part of the proceeds from all sales go to support the Canadian Obesity Network)

If you have already read Best Weight, please take a few minutes to leave a review on the Amazon or Barnes & Nobles website.