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Sunday, January 1, 2017

Think sweet ~ stay slim

Think sweet ~ stay slim

Notwithstanding the overwhelming evidence that an excess of calorie intake per se, irrespective of the source of calories, causes obesity, there remains a populist and a policy view that sugar, rather than fat is the primary culprit. Although the biological argument that not all calories are equal and that carbohydrate calories are more fattening has been debunked by sound experimental evidence[1], the case moves more to appetite as the causative factor. Since people don’t eat what they don’t like, an understanding of the “liking” of particular foods becomes important.

To study this phenomenon, two approaches are possible. One is to use a ‘cross sectional’ approach which seeks to compare obese persons and lean persons for their food preferences at a single moment in time. The problem here is that the obese persons may have acquired a view of what putatively ‘causes’ obesity and in so doing, they may bias their response to any study questionnaires. Thus obese subjects at a given point in time might express a lower liking for sugar-sweetened beverages compared to diet beverages because that is what they are conditioned by society to believe. Moreover, obese subjects may in fact use sugar free beverages to manage their weight. The alternative to this approach is to complete a ‘prospective’ study in which people’s likings for food are measured at a single point in time and the group subsequently followed over several years to see who gets obese and who stays slim. That way, the presence of obesity is independent of the answers to the original questionnaire.

A recent paper from the French research consortium “NutriSanté” has examined the effect of liking for fat, sugar and salt on subsequent development of obesity[2]. The NutriSanté study is an internet-based study, initiated in 2009, with a current enrolment of some 65,683 volunteers. Data is gathered at the point of recruitment on many aspects of health such as diet, physical activity, weight, smoking and alcohol habits, weight management and so on and is repeated annually.  Each month, volunteers are invited to complete questionnaires related among other things to food behaviour.  The questionnaire covered salt (11 questions) and sweet (21 questions) tastes plus preferences of fat-and-salt (31 questions) and fat and sweet sensations (20 items).  Some 49,066 subjects agreed to answer these questions. However, when the data were cleaned up to ensure that all respondents had completed every aspect of the overall NutriSanté study, there were full data on 24,776 subjects.

In the 4 years of follow up, 24,112 subjects remained non-obese while 664 subjects became obese. The key sensory findings are thus:

Sensory liking scores
Non-obese subjects
Obese subjects
Statistical conclusions
Liking for fat
Highly different
Liking for sweet
No difference
Liking for salt
Highly different

Those who gained weight had a higher preference for fat and salt but not for sugar.  Another approach to the data analysis is to look across the “liking” score data and to divide subjects according to their ranking, starting at the “low liking” (lowest quarter or ‘quartile’) right up to the “highest liking”  (highest quartile). These data are controlled statistically for all known confounding variables.

Statistical difference in risk of developing obesity between lowest and highest quartiles of “liking”

Fat liking
Yes, up 85%
Yes, up 49%
Fat + salt liking
Yes, up 106%
Fat + sweet liking
Yes, up 37%
Sweet liking
Yes, down 59%
Natural sweetness liking
Yes, down 69%

The authors also looked at baseline food intake (as opposed to liking) and observed no association between sugary food intake and obesity. Indeed, the evidence was that those who did not develop obesity had higher sugar intakes at baseline. The results are summarised below.

Food group intake g/d
Non-obese subjects
Obese subjects
Statistical conclusions
Highly different
Highly different
Processed meat
Highly different
Milk and yogurts
Highly different
Not different
Highly different
Whole grain products
Highly different
Sugar and products
Highly different
Fatty sweet products
Not different
Sugar-sweetened soft drinks
Not different

The authors conclude thus: “This prospective study reinforced results from cross sectional studies, by highlighting that fat liking was prospectively associated with an increased risk of obesity and diet appeared to substantially explain this relationship. Results have also shown that sweet liking is associated with a decreased risk of obesity, and there is no significant association between salt liking and obesity risk”.

Once again, we have a fully public funded comprehensive and prospective study from a highly reputable group, with the study suitably powered for optimal statistical analysis, which challenges conventional wisdom. It will be ignored but, you see, it won’t go away and one day, when the false gods of the demonic sugar sect are reduced to clay, these papers will come back to haunt the high priests of public health nutrition. I wanna be there!!!

By the way, the blog stands now at 231,325 views. Thank you all and a happy New Year to all of you.

[1] See blogs of November 21st 2016 and of August 14th, 2015.
[2] Lampuré et al. International Journal of Behavioral Nutrition and Physical Activity (2016) 13:74

Tuesday, December 27, 2016

Diet and poverty: Mind over money?

Diet and poverty: Mind over money?

Obesity is popularly linked with low-income groups and with a low socio-economic status (SES). This relationship is frequently explained by a lack of money, a lack of understanding of healthy nutrition, a general disdain for healthy eating and both isolation from supermarkets and proximity to convenience and fast food outlets. I won’t argue with this except to say that while obesity is more prevalent in low SES, there are a lot of fat judges, mayors, prime ministers, presidents elect, ex-sportsmen, doctors, nurses and others for whom the putative drivers of obesity in poverty are generally absent. New research[1] on obesity and SES has recently been published by scientists from Singapore’s A*STAR and published in the prestigious journal, The Proceedings of the National Academy of Sciences. The key question they asked was thus: Irrespective of your true SES, if you were made to think you were of a low SES, would that influence your food habits?

They started their thinking process with reference to the animal kingdom where in any social organisation, those that are marginalized for whatever reason (too slow, too weak, too fussy), also tend to overeat and gain weight. This might be a precaution for survival in the event that they might one day be in fact ousted from the group. They cite a hamster study where a smallish hamster living in harmony with other small hamsters is placed alone in a cage into which a larger hamster is admitted. The latter will assert itself as dominant within less than a minute and the  “defeated” smaller hamster is left to sulk. The plot of body weight over time comparing those hamsters subject to defeat against those spared this ignominy shows that the defeated hamsters, stigmatized and “psychologically” marginalised, get fatter.

Against that background from the animal kingdom of which the hamster data is merely illustrative of so many such studies, they set out to study if an “imagined” low SES could alter food habits.

The human volunteers were placed in a private room and the study was conducted in what were effectively laboratory conditions. They were shown a ladder with the following instructions:

Think of this ladder as representing where people stand in Singapore. Now, please compare yourself to the people at the very top of the ladder. These are the people who are the best off—those who have the most money, most education, and most respected jobs. In particular, we’d like you to think about how YOU ARE DIFFERENT FROM THESE PEOPLE in terms of your own income, educational history, and job status. Where would you place yourself on this ladder relative to these people at the very top? Please select the number that corresponds to the rung where you think you stand in relation to these people.

 A second group was similarly treated but they compared themselves to people at the bottom of the ladder: poor, less education and rotten jobs. To emphasise the mental induction of subjective higher or lower SES, subjects had to write down in detail how a conversation might go with the group above or below themselves and to suggest how such a conversation might flow. Now, suitably indoctrinated into a feeling of subjective high or low SES, the experiments began and the easiest way to communicate the studies is to simply focus on the results.

  • When asked to select the foods they might be subsequently included in a meal, those who subjectively thought of themselves as lower SES, chose higher energy dense foods and overall indicated an intention to eat more calories than those who were attuned to think of themselves as higher SES
  • When asked to rate foods according to descriptors such as pleasant (e.g., tasty, delicious, wonderful) and unpleasant (e.g., disgusting, nasty, awful) those in the lower SES subjective state chose the higher energy density foods as the most pleasant
  • In a third study, the subjects viewed a short documentary video while freely eating three snacks (potato chips, M&M candies, and California raisins) from separate bowls. Those with the lower SES frame of mind ate more calories and they more or less favoured the chips and M&Ms over the raisins.
  • Finally, the subjects were given access to a meal in the form of noodles and asked to eat to appetite. For completeness, a control group who did not take part in the imagined SES ranking exercise was included. The outcome showed that those who subjectively rated themselves as lower SES ate significantly more then the other two groups.

These studies were carefully designed and the analysis took statistical account of all key variables (age, gender, weight etc.) including the actual SES of the subjects. The results could be interpreted thus: When induced to think they are of a low SES, people overeat because that’s what they think those of low SES actually do. However, there are a few reasons to downplay this potential explanation. First, each experiment involved different volunteers so there could be no sense of training. Secondly, food was not portrayed as a central element of the study but rather the self-imposition of a state of mind. Finally, and most importantly, those induced to imagine themselves as low SES, were comparing themselves to those at the top of the social ladder who were the economic elite.

So, once again, we see what we refer to as the “mind” playing a driving role in one of nature’s most powerful biological drives, the drive to eat[2].

[1] Cheon BK & Hong Y-Y (2016) Mere experience of low subjective socioeconomic status stimulates appetite and food intake Proceedings of the National Academy of Sciences (Early edition)
[2] Mind over matter: Perceived time as opposed to real time on blood glucose in type 2 diabetes: Blogged October 14th 2016