|Food variety increases binge eating risk, studies show.|
- Sugar-Sweetened and Artificially-Sweetened Beverages in Relation to Obesity Risk - In his latest review, Mark A. Pereira set out to "critically evaluate the scientific evidence in humans on the potential effect of sweetened beverages on weight gain and risk of obesity in youth and adults" (Pereira. 2014).
In particular, he compared the association of sugar-sweetened beverages (SSBs) include soft drinks, colas, other sweetened carbonated beverages, and fruit drinks with added sugar and their artificially sweetened counter-parts on obesity risk - with an expected outcome:
"The totality of evidence to date demonstrates a pattern across observational and experimental studies of an increased risk of weight gain and obesity with higher intake of SSBs" (Pereira. 2014).The actual problem is that it is difficult to establish the strength of the association and the independence from other potentially confounding factors. In that, Pereira highlights that the primary reason for unclear conclusions regarding the robustness of any effect of SSBs is due to the heterogeneity and methodologic limitations of both observational and experimental studies on this topic.
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More specifically, none of the currently available epidemiologial studies was able to make sure that the associations the scientists observed were not the result of reverse causality, i.e. obese people consuming artificially sweetened beverage, because they are (already) obese and not the other way around. As Pereira points out, this is more than just a theoretical issue, "higher-quality studies demonstrate this possibility" (Pereira. 2014).
Accordingly, the field needs "higher-quality experimental studies in humans, with relevant direct comparisons between sweetened beverages and their sweetened solid-food alternatives" (Pereira. 2014).
- Food Availability/Convenience and Obesity - Penny Gordon-Larsen reviewed the ever-increasing number of studies investigating the impact of certain qualities of the neighborhood environments on obesity risk. As Gordon-Larsen points out, "there are inconsistencies in the evidence base, suggesting a nuanced association between neighborhood environment, food availability, diet behaviors, and obesity" (Gordon-Larsen. 2014).
With the currently available evidence being limited by a predominance of cross-sectional studies, a high reliance on commercial business listings, a lack of attention to the process by which diet resources are established and expanded within neighborhoods and the potential for individuals to selectively migrate to locate near such facilities, it is difficult to make a reliable conclusion with respect to the influence of food availability and convenience on obesity risk.
Against that background it is difficult to tell, whether the results of a recent study from New York which shows that there is an inverse association between BMI and food outlet density (−0.32 BMI units across the IQR, 95% CI −0.45 to −0.20) is actually significant.
Figure 1: Adjusted association between body mass index and food environment measures (Stark. 2014)
- Food Prices and Obesity - is there a link? As a SuppVersity reader you will know that politics and researchers have repeatedly been debating about taxes on unhealthy foods. To estimate, whether these taxes would work, we would yet have to know "the extent to which overall energy intake or weight outcomes" are actually influenced by food prices.
"the current evidence indicates that, by themselves, targeted food taxes and subsidies as considered to date are unlikely to have a major effect on individual weight or obesity prevalence." (Finkelstein. 2014)Unlike the researchers I am thus not really optimistic that "food taxes and subsidies may play an important role in a multifaceted approach to reducing obesity incidence" (Johnson. 2014) - in particular, if the taxes are determined in accordance with the current US food pyramid, so that "healthy grains" are not taxed at all and "unhealthy eggs" are taxed in a way that even an "industrially" produced egg will costs a dollar.
- Evidence for Efficacy and Effectiveness of Changes in Eating Frequency for Body Weight Management - As Ashima Kant point out, in self-reported diets of free living individuals, frequent eating is associated with higher energy intake. In spite of the scientific evidence, beliefs about the possible beneficial effect of higher eating frequency for managing body weight persist.
In her review of prospective cohort studies and controlled trials of manipulation of eating frequency published by 31 December 2012, Kant included four prospective cohort studies were identified - 2 of these included adults followed for 10 y and 2 followed pre-adolescent / adolescent girls for 6 or10 y.
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"Six controlled trials with adult subjects serving as their own controls found no significant changes in body weight due to manipulation of eating frequency interventions lasting 6–8 wk."In six additional intervention trials of 8–52 wk duration, free-living adults were counseled to change the eating frequency of self-selected food intake with no significant differences in weight loss attributable to eating frequency.
Currently, the overwhelming majority of the available evidence does thus suggest that manipulation of eating frequency will not promote weight loss. The available scientific evidence is thus once more in conflict with common belief about "best practice", when it comes to losing weight - a "common belief", by the way that was, as so often, influenced by epidemiological data of which people simply don't understand that it cannot establish reliable causal relationships.
- Portion Size and Obesity - In their review of the contemporary literature on the effects of portion size on obesity and weight control, M. Barbara E. Livingstone and L. Kirsty Pourshahidi leave little doubt that "portion size has a powerful and proportionate effect on the amount of food consumed." (Livingstone. 2014).
In spite of the fact that the positive effect of portion size on energy intake has been demonstrated for different types of foods and beverages, and is particularly pronounced with energy-dense foods, though, it is as of now not clear what types of interventions targeted at portion size are likely to be effective, in what settings, and among which target groups.
Figure 2: You don't need to conduct a study to realize that portion sizes for foods and beverages - specifically the unhealthy ones - are ever-increasing (image from scienceinseconds.com)
- Variety and Palatability - Reasons We Get fat? As Fiona Johnson and Jane Wardle point out, "among the key characteristics of the Western obesogenic food environment is a highly palatable and varied food supply" (Johnson. 2014). At first, this sounds yummy and healthy. Unfortunately, the possibility to switch back and forth between a large variety of highly palatable salty and sweet junk food has been shown in both humans and animals to
(a) have appetite stimulating effects, to (b) delay satiety, and to (c) promote excessive energy intake.
Figure 3: When men are offered a sandwiches with identical or varied (4 different) fillings, they will consume significantly more if they are allowed to switch back and forth between the different fillings (Rolls. 1981).
"However, laboratory paradigms do not replicate the complexities of eating in a natural setting [...and t]here are substantial individual diffe- rences in susceptibility to the palatability effect and this may be a key determinant in individual vulnerability to weight gain" (Johnson. 2014).Or, put more simply, as long as we do not fully understand the pathways through which palatability and variety can affect eating, it is difficult to identify what helps those who can abstain from overeating maintain their weight and what we can do for those who fall for the temptations to help them stand the test of chocolate, chips, pizza and beer.
- Finkelstein et al. "Food Prices and Obesity: A Review." Adv Nutr. 5 (2014): 818-821.
- Gordon-Larsen, Penny. "Food Availability/Convenience and Obesity". Adv Nutr 5 (2014):809-817
- Johnson, et al. "Variety, Palatability, and Obesity." Adv Nutr. 5 (2014): 851-859.
- Kant, Ashima K. "Evidence for Efficacy and Effectiveness of Changes in Eating Frequency for Body Weight Management." Adv Nutr 5 (2014): 822-828.
- Livingstone, et al. "Portion Size and Obesity." Adv Nutr. 5 (2014): 829-834.
- Mytton, Oliver T., Helen Eyles, and David Ogilvie. "Evaluating the Health Impacts of Food and Beverage Taxes." Current Obesity Reports (2014): 1-8.
- Pereira, A. P. "Sugar-Sweetened and Artificially-Sweetened Beverages in Relation to Obesity Risk." Adv Nutr 5 (2014): 851-859.
- Rolls, Barbara J., et al. "Variety in a meal enhances food intake in man." Physiology & Behavior 26.2 (1981): 215-221.
- Stark, James H., et al. "Neighbourhood food environments and body mass index among New York City adults." Journal of epidemiology and community health 67.9 (2013): 736-742.