I’ve written about aspartame before and a lot of the Utter, Utter Bollocks (µ²B) claimed of it. Now a new study has been published claiming diet soda causes obesity that lazy journalists and the Warriors of Woo will all be seizing upon.
The study, published in the Journal of the American Geriatrics Society, makes the claim that increasing diet soda intake is directly linked to greater abdominal obesity in adults 65 years of age and older. They therefore raise concerns about the safety of chronic diet soda consumption with the inference it may increase belly fat and contribute to greater risk of metabolic syndrome and cardiovascular diseases. But they seem to have forgotten correlation is not causation.
Metabolic syndrome – a combination of risk factors that may lead to high blood pressure, diabetes, heart disease, and stroke – is one of the results of the obesity epidemic we are seeing in the developed world. The World Health Organization estimates that 1.9 billion adults are overweight (defined as a BMI of 25 or more) and of this group 600 million fall into the obese category (BMI of 30 or more) – a figure that has more than doubled since 1980.
It is suggested that in an effort to combat obesity, many adults try to reduce sugar intake by turning to non-nutritive / artificial sweeteners such as aspartame. Research shows that in the past 30 years artificial sweeteners and diet soda intake have increased, as has the prevalence of obesity. Other studies have explored diet soda consumption and cardiometabolic diseases in middle-aged and younger adults; this new one looked at the elderly.
The San Antonio Longitudinal Study of Aging (SALSA) enrolled 749 Mexican- and European- Americans who were aged 65+ at the start of the study (1992-96). Diet soda intake, waist circumference, height and weight were measured at study onset, and followed up for almost a decade. At the first follow-up there were 474 (79.1%) surviving participants; there were 413 (73.4%) at the second follow-up and 375 (71.0%) at the third follow-up.
The data show that the increase in waist circumference among diet soda drinkers (per follow-up interval) was almost triple that among non-users. After adjustment for potential confounders interval waist circumference increases were 0.77 cm for non-users, 1.76 cm for occasional users, and 3.04 cm for daily users. This translates to waist circumference increases of 2cm for non-users, 4.6cm for occasional users, and 8cm (3 inches in old money) for daily users over the total 9.4-year follow-up period. While the study is of a decent size this isn’t really a stellar increase in girth, even in the ‘daily’ group.
“The SALSA study shows that increasing diet soda intake was associated with escalating abdominal obesity, which may increase cardiometabolic risk in older adults” and the authors recommend that older individuals who drink diet soda daily – particularly those at high cardiometabolic risk – should try to curb their consumption of artificially sweetened drinks.
Which I find rather naïve for a number of reasons…
First off this is a longtitudinal study and inferring causality – even from the best longitudinal studies – has serious limitations. There are just too many confounding variables. And if correlation is causation you will see from the graph on the right that the real cause of autism is organic foods, not vaccines.
Second, a 2″ over ten years? And they come up with some very precise measurements and waistline is a tough thing to measure consistently or accurately. The authors also suggest diet soda ‘disturbs people’s internal rain forests’ thus causing fat accumulation. Puhleeeeeze….
Finally, from my own observational data in many US fast food joints, the 48oz diet soda tends to accompany a triple-supersized burger with a mountain of fries. People seem to think that having a ‘diet’ drink with their Cholesterol Special somehow offsets or negates the calories consumed. Which is clearly Utter, Utter Bollocks (µ²B).
And even in the UK there is a 2,000 Calorie burger – which equates to half a pound of body mass even before you factor in the fries. (Yes, the 3,500 kcal per lb body mass is an approximation with a bunch of caveats but it’s not a bad heuristic).
So, do diet drinks cause obesity? No. Excess calories and other lifestyle factors cause obesity and while there may be a correlation in this study it’s a long way from the causation much of the press coverage claims…