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Monday, November 21, 2016

Fat calories count most in obesity ~ new study

Conventional wisdom, at least from the media and the high priests of public health nutrition, tells us that sugar causes obesity and all its ailments to the point where it is likened to tobacco in its sinister provenance and its foul health implications. Sugar is to be taxed and restricted in every way and politicians of all persuasions win popular support for their call for yet more extreme measures to decry the putative effects of sugar. And all the time, this conventional wisdom is promoted by the media and by celebrity chefs and diet gurus.. So it should come as no surprise that when a study from a high quality group using high quality data, publish a high quality paper in a high quality journal, which flies in the face of conventional wisdom, that this fine data, is simply ignored.

The paper[1] is based on data from the UK Biobank database that tracks individuals over time (2011 and 2012). It uses direct measures of body weight and height and classified the 132,479 subjects into underweight, normal weight, overweight and obese with obesity further divided into grades I, II and III obesity. Data were also obtained for each subject on % body fat and on waist circumference. Dietary data was collected using four 24-hour recalls over 2011 and 2012. Subjects were excluded from the study if there was any possibility that their diet or weight might be compromised in some way. For example, smokers, who tend to be under-weight, were excluded, as were those with a reported energy intake deemed by international norms to indicate under-reporting of calorie intake.

The bottom line in the findings was that moving across increasing grades of either body weight or body fat, energy intake, as in calories per day, also increased. As I have previously paraphrased US President Bill Clinton in his election campaign: “It’s the calories, stupid!” Compared with normal BMI, obese participants had 11.5% higher total energy intake and 15%, 14%, 10% and 5% higher intake from fat, protein, starch and sugar, respectively. Hence, the proportion of energy derived from fat was higher (34.3 v. 33.4) but from sugar was lower (22.0 v. 23.4).

This simply tells us there is a direct positive association between calorie intake and rising levels of overweight. A key question remains as to the contribution of fat and carbohydrate (with sugar specifically in mind) to obesity when we statistically control for the calorie intake. The authors thus transformed the data to control for the following: sex, ethnicity, physical activity and calorie intake.  This allows us look at data where fat intake and sugar intake are examined for their links to obesity where caloric intake is controlled to a common level. Now we see that when sugar intake and starch intake (all carbohydrates) are compared across rising levels of obesity, they actually fall. In contrast, fat rises. This isn’t anything new because when energy intake is fixed at a constant point, as one contributor to caloric intakes rise (e.g. fat) others, (carbohydrates including sugar) falls, a fact recorded so many times (the sugar-fat see-saw) and so repeatedly ignored by the anti-sugar lobby.  The figures below are taken from the journal where quintiles if nutrient intake are compared to BMI.

The authors conclude as follows from their research:

 Key Messages
• Adiposity is associated with higher intake of sugar; but the association is stronger for fat intake and strongest for total energy intake.
• Fat is the largest contributor to overall energy intake.
• There is only a weak correlation between absolute energy derived from sugar and from fat. Therefore, targeting high sugar consumers will not necessarily target high consumers of fat and overall energy.
• Focusing public health messages on sugar consumption may mislead the public on the need to reduce fat intake and overall energy intake.
This was a study funded by a University of Glasgow internal grant and was not funded by the sugar lobby nor have the authors any conflict of interest to report. But it doesn’t conform to conventional wisdom so it will largely remain ignored by the media and senior policy makers will find it awkward reading, if at all, because they have already followed the herd of the anti-sugar lobby.

[1] Andersen JJ (2016) Adiposity among 132 479 UK Biobank participants; contribution of sugar intake vs other macronutrients. International Journal of Epidemiology, 2016, 1–10

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