Yesterday, I posted about the interesting study by Madjd and colleagues suggesting that drinking water may be better for weight loss than drinking diet beverages.
But what exactly is the evidence that low-calorie sweeteners (of which there are many) may actually have non-caloric effects on energy intake or body weight?
The authors assessed both animal and human studies involving the consumption of low-calorie sweeteners in conjunction with an ad libitum diet.
In 62 of 90 animal studies exposure to low-calorie sweeteners did not affect or decreased body weight. Of 28 studies that did report increased body weight, 19 compared compared low-calorie sweeteners with glucose exposure using a specific ‘learning’ paradigm.
In humans, 12 prospective cohort studies found inconsistent associations between the use of low-energy sweeteners and body mass index, with overall minimal effects at best.
A meta-analysis of short-term randomized controlled trials (involving 129 comparisons) showed reduced total energy intake for low-calorie sweetener versus sugar-sweetened food or beverage consumption before an ad libitum meal (about −94 kcal per day), with no difference versus water (−2 kcal per day).
These findings were consistent with energy intake observations in sustained intervention randomized controlled trials (10 comparisons), a meta-analysis of which (with study durations ranging from 4 weeks to 40 months) showed that consumption of low-calorie sweeteners versus sugar led to relatively reduced body weight (nine comparisons), and a similar relative reduction in body weight compared to water (three comparisons).
Thus, contrary to what is often stated in popular media or even by some experts, there is little if any evidence either from animal or human studies that the use low-caloric sweeteners has any measurable impact on energy intake (other than reducing total caloric intake) or body weight.
Thus, the authors conclude that
“Overall, the balance of evidence indicates that use of low-energy sweeteners in place of sugar, in children and adults, leads to reduced energy intake and body weight, and possibly also when compared with water.”
Obviously, even this analysis is not going to silence the sceptics, who will continue to claim that somehow low-calorie sweeteners are still messing up your energy intake or metabolism.
However, it may be fair to conclude that if indeed such effects exist, their magnitude is likely marginally and of doubtful clinical significance.
I will continue recommending that my patients do their best to replace sugar with non-caloric sweeteners if giving up their liking for sweet foods or beverages is not an option.
According to conventional wisdom, beverages with artificial sweeteners should be weight neutral, given that they do not contain calories. However, whether this is true or not remains controversial. Besides the epidemiological evidence suggesting that the consumption of artificially sweetened beverages may be associated with higher body weights, there are also a range of physiological studies suggesting that artificial sweeteners can induce metabolic changes (including changes in taste preferences) that may promote weight gain.
Now, a study by Ameneh Madjd and colleagues from the University of Nottingham, UK, and the Tehran University of Medical Sciences, Iran (where the study was conducted) published in the American Journal of Clinical Nutrition, suggests that replacing ‘diet beverages’ (DBs) with water may not only result in greater weight loss but may also have greater benefits in terms of glucose metabolism.
The study was conduced in 89 women with overweight or obesity who usually consumed DBs in their diet.
Participants were randomized to either replace their DBs with water or continue drinking DBs 5 times/wk after their lunch for 24 wk (DB group) while on a 24-week weight-loss program.
71% of participants completed the trial (32 in the DB group, 30 in the water group).
Over the 24 weeks, the water group lost about 1.2 Kg more than the DB group (mean weight loss of both groups was about 8 Kg).
Improvements in fasting insulin levels, HOMA index and 2-hr post-prandial glucose also tended to be greater in the water than in the DB group.
Thus, the authors conclude that replacement of DBs with water after the main meal may lead to greater weight reduction and more favourable metabolic benefits during a weight-loss program.
As for the possible mechanisms that would account for these findings, the authors speculate based largely on self-reported changes in food intake that the water-drinking group may have been more compliant to the recommended diet and may have marginally reduced their carb intake. There is also the possibility that drinking water (rather than DBs) may support weight loss through other mechanisms.
Overall, I am not sure what to really make of this study. Clearly, being able to replace DBs with water may be beneficial. On the other hand, the more common problem in my practice is dealing with patients who consume larger amounts of sugar-sweetened beverages (SSBs rather than DBs) and I would imagine that if a shift to water is too drastic, DBs may at least be substantially better than continuing on with SSBs for these patients.
Changes in caloric balance are long known to affect metabolic requirements – in general, overfeeding tends to increase metabolic rate, whereas underfeeding (or fasting) tends to lower metabolic rate. However, the magnitude of these changes tend to vary substantially between individuals.
Now a study by Martin Reinhardt and colleagues, published in the International Journal of Obesity, shows that this variation in response to overfeeding and fasting may predispose some individuals to obesity (thrifty phenotype).
Firstly, the researchers found that a greater %EE decrease with fasting correlated with a smaller %EE increase with overfeeding, or in other words, individuals who responded with a greater decrease in caloric expenditure in response to fasting also showed a lower increase in caloric expenditure with overfeeding.
The %EE decrease with fasting was associated with both fat mass and abdominal fat mass as well as a lower 24-hour core body temperature (even after accounting for a number of covariates). A 0.1°C lower core body temperature was associated with a 1.4% greater decrease in EE during fasting.
From these findings the authors conclude that,
“body temperature may be a further defining feature of the human thrifty phenotype and offer insight into contributors to the inter-individual variation observed in energy expenditure responses to caloric restriction or excess.”
They also suggest that perhaps careful measurements of body core temperature could be harnessed to direct weight loss or weight maintenance efforts during life style interventions.
If nothing else, the study nicely documents that we are not all equal when it comes to how our bodies respond to over or underfeeding.
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WHEREAS: The disease of obesity is a major source of concern across the nation. In California, the adult obesity rate is nearing a quarter of the population (24.7%) and in Los Angeles County, the percentage of adults affected by obesity continues its steady rise from 13.6% in 1997 to 24.3% in 2013, and
WHEREAS: Experts and researchers agree that obesity is not a lifestyle choice but rather, a complex disease influenced by various physiological, environmental factors, and
WHEREAS: While prevention programs, including the 2010 California Obesity Prevention Plan, have successfully established the seriousness of this public health crisis, it is also imperative that individuals and families currently affected by obesity receive comprehensive care and treatment, and
WHEREAS: Studies show that bias and stigma against people affected by obesity among general society and healthcare professionals are significant barriers to effectively treating the disease, and
WHEREAS: Healthcare professionals must treat patients with respect and compassion, and partner with patients to develop a comprehensive and individualized approach to weight-loss and weight management that considers all appropriate treatment options such as reduced-calorie diet and physical activity modifications, pharmacotherapy, or bariatric surgery, and
WHEREAS: It will take a long-term collaborative effort, involving partners from across all fields – individual, corporate and institutional – taking an active role, to ignite the betterment of obesity care and treatment:
NOW, THEREFORE, I, ERIC GARCETTI, as Mayor of the City of Los Angeles, and on behalf of its residents, do hereby proclaim the week of November 1-7, 2015 as Obesity Care Week in the City of Los Angeles, and encourage all our citizens to create the foundation of open communication to break barriers of misunderstanding and stigma, and improve the lives of all individuals affected by obesity and their families.
September 25, 2015
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As Canada’s national representative in the World Obesity Federation (formerly IASO), the Canadian Obesity Network is proud to co-host the 13th International Congress on Obesity in Vancouver, 1-4 May 2016.
The comprehensive scientific program will span 6 topic areas:
Track 1: From genes to cells
- For example: genetics, metagenomics, epigenetics, regulation of mRNA and non–coding RNA, inflammation, lipids, mitochondria and cellular organelles, stem cells, signal transduction, white, brite and brown adipocytes
Track 2: From cells to integrative biology
- For example: neurobiology, appetite and feeding, energy balance, thermogenesis, inflammation and immunity, adipokines, hormones, circadian rhythms, crosstalk, nutrient sensing, signal transduction, tissue plasticity, fetal programming, metabolism, gut microbiome
Track 3: Determinants, assessments and consequences
- For example: assessment and measurement issues, nutrition, physical activity, modifiable risk behaviours, sleep, DoHAD, gut microbiome, Healthy obese, gender differences, biomarkers, body composition, fat distribution, diabetes, cancer, NAFLD, OSA, cardiovascular disease, osteoarthritis, mental health, stigma
Track 4: Clinical management
- For example: diet, exercise, behaviour therapies, psychology, sleep, VLEDs, pharmacotherapy, multidisciplinary therapy, bariatric surgery, new devices, e-technology, biomarkers, cost effectiveness, health services delivery, equity, personalised medicine
Track 5: Populations and population health
- For example: equity, pre natal and early nutrition, epidemiology, inequalities, marketing, workplace, school, role of industry, social determinants, population assessments, regional and ethnic differences, built environment, food environment, economics
Track 6: Actions, interventions and policies
- For example: health promotion, primary prevention, interventions in different settings, health systems and services, e-technology, marketing, economics (pricing, taxation, distribution, subsidy), environmental issues, government actions, stakeholder and industry issues, ethical issues
Early-bird registration is now open – click here
Abstract submission deadline is November 30, 2015 – click here
For more information including sponsorship and exhibiting at ICO 2016 – click here
I look forward to welcoming you to Vancouver next year.