Friday, January 18, 2013

Study Reveals Unsettling Data About How Fat We've Gotten Over the Past 40 Years. Plus: Macronutrient Analysis of the Diets of Leanest & Fattest Yields Surprising Results

Man, the 70s that was a time! A time, when the average American still had a 20% lower BMI, being normal weight was still the norm and models like those in the photo above did not have to be anorexic.
I used to hate it, when old people said that "back in the good old days, everything used to be much better"... one thing, however, certainly was better. The physical health and shape people were in. According to a paper that's been published ahead of print in the journal Public Health and Nutrition, the NHANES data from 1971-2004 clearly shows that the BMI of the average US citizen has risen by ~3pts over this 13-year period and if the trend continued in the years after, we should by now be hovering 4-5pts higher than in 1971-1974, when a BMI of 25.58 kg/m² for men and 25.01 kg/m² for women was the norm.

Let's take a look at data

I am actually not sure where to start with my detailed recapitulation of the data, but I guess there is no direct causal relationshipp between the decline of marriage rates (75%-57.5%; averages) from the early 1970 to the early 2000s that's to blame, so that's probably not the best starting point. In fact, if you look closely, the trigger must be somewhere in the late 1980s, early 1999, where the BMIs literally exploded andthe number of "lightly" obese individuals previously hovering around at 7% doubled -  a timpoint at which the decline in marriage rates from the late 1970s was already over and the marriage rates remained more or less stable, by the way ;-)
Figure 1: Mean BMI  (kg/m²; right axis) and BMI class (values in %, BMI classes from <18.5kg/² = underweight to >40kg/m²  = morbidly obese; left axis)  development in the US; data based on averages calculated based on NHANES data from men and women (Yancy. 2013)
So, not being married can hardly be responsible for the fact that being obese is already the new "normal" in the US. And though I think that we are rather going to eat us to death, than being struck by plagues (or the flu ;-) or an asteroid or whatever, he obesity explosion did not coincide with the end of the Maya calender, either (see figure 1, right).

You can of course still argue that by adding the overweight Americans to the equation the obese US boys and girls would be a minority again, but the simple fact that the number of overweight individiuals remained constant while the number of normalweight Americans was constantly declining tells you that being overweight is nothing but a transient state from normal to obese, these days. It's nothing people will remain in for their whole life - in most cases probably not even for more than one or two years, although many are trying hard to change things.
Figure 2: While more and more US men and women say that they are trying to lose weight (left), the average American keeps eating more and more every year (Yancy. 2013)
No wonder this does not work, when the average average American (esp. the average US man) keeps upping his caloric intake (see figure 2, right), while the hilariously unreliable physical activity data tells us that the amount people moved stayed about the same, while the difference between fitness junkies and total sloths increasing (data not shown).

People love it, but is it really true, "calories don't count"?

It's as easy as the pie that's going down your piehole: At the end of the day, calories do count and magic pills and single-sided diets are not going to save "the average American" from drowning in his / her own blubber, if he  / she does not accept that "super-size meals" generate "super-size people". On the other hand, the current understanding that differences in the +/- 100kcal  would make a significant difference, is intrinsically flawed, scientifically not sustainable and totally disregards the importance of what you eat, how (not how much) you exercise, how and how much you sleep, how much stress you have and so on and so forth... Unfortunatelythe majority 2000-2004 NHANES cohorts of US citizens did not make the good food choices, do the concomitant strength and cardio workouts, are almost anal about their sleep hygiene and keep a constant eye on their stress levels that would allow them to get away with eating constantly 10% more than their predecessors in the 1971-1974.
Figure 3: Changes in macronutrient composition of "the American diet" (Yancy. 2013)
Apropos "healthy food choices", maybe it's just that people don't follow the glorious advice from their government on what to eat that's making them fat - ha? Well, if you look at the data in figure 3 you will seee that women are slightly more compliant to the "eat more carbs, cut your fats" mantra, but as we are going to see neither their nor their male peers "non-compliance" can explain the 10% difference that exists between the increase in caloric intake (+10%) and the 20% increase 20% in BMI from the 1970s to the early 2000s. Moreover, a differential analysis of the macronutrient intakes according to BMI classes yielded only one significant observation and that's not exactly in favor of eating more fat (allegedly most likely the wrong, namely high n-6 fats from "good" vegetable oils):
"In men, the proportion of total energy intake from carbohydrate declined with increasing BMI category (46.6 % in underweight/normal weight to 45.5 % in obese class II/III, P<0.01 for trend), after adjusting for survey period and other variables. In women, the decline across BMI classes was slighter (0.4 percentage points) but still statistically significant (P<0.01 for trend)." (Yancy. 2013)
The opposite goes for the trends for fat intakes, which are positive with the leanest getting the least amount of their daily energy requirements from fat. Needless to say that the NHANES data does not tell us, where these fats and carbohydrates came from. Still the scientists kick of their conclusion stating that:
"You told me to eat more protein and this burger has both meat and cheese!" - This and other mishaps are the reasons why calories still count in the books of most dietitians - read more about "What Really Happens When Science Meets Real Life"
"From 1971 to 2004 in the USA, daily energy intake and the percentage of daily energy from carbohydrate increased substantially, whereas the percentages of daily energy from fat and protein declined. These results are consistent with a prior study that did not adjust for the full set of demographic, health status, physical activity and dietary behaviour variables considered here (Austin. 2011). The types of foods that explain these changes in macronutrient composition in the American diet were not a focus of the present study, but previous research has demonstrated that intakes of sugared beverages and fast foods increased substantially over the time period of the surveys (Nielsen. 2003) . The decline in percentage of daily energy from fat may indicate that the US population altered dietary intake in response to the USDA’s messages to reduce dietary fat. Unfortunately, the decrease in percentage fat intake was more than compensated with an increased intake of carbohydrate that was predominantly refined starches and sugars (Nielsen. 2003)." (Yancy. 2013)
Actually the researchers could have concluded their paper right here, if their own differential analysis had confirmed what appears to follow naturally from the above, namely that those who are the fattest will eat the most carbs and the least fat. That's however not the case. And if this was not already paradoxical enough, the obese individuals "reported" consuming an  overall lower amount of energy, as well. So, ...
"[t]hese results suggest that obese individuals did not, as one would expect from our current understanding of maintenance energy requirements, consume more energy than their underweight/normal weight peers, nor did they consume diets that were dramatically different in macronutrient content. [...] For example, using an equation commonly used for calculating energy requirements, a 45-year-old sedentary man of average height (1,78 m) who weighed 70 kg (BMI=22.0 kg/m²) would require 9606 kJ/d to maintain that weight; a man of the same age, height and activity level who weighed 120 kg (BMI=38.0 kg/m²) would require 12.962 kJ/d, a difference of ~3347 kJ/d. This contrasts with the finding in the current study that adjusted energy intakes in the lowest and highest BMI classes differed by only 209–1255 kJ/d in each of the surveys" (Yancy. 2013)
And while Yancy et al. mention under-reporting and (this is a certain plus of the study) acknowledge that you can lose fat with both high carb and low carb diets, they miss one very import point, which is the vicious cycle of obesity induced metabolic malfunction. Once you are fat chronic inflammation, insulin resistance, the inability to exercise properly, depression and all the other miseries will help hamper your bodies natural weight regulation mechanisms and you end up gaining weight even if your dietary records are not flawed and you are actually eating less than you would theoretically need if you were a healthy 120kg man with a normal body fat content somewhere in the 14-18% range

I guess most of you will probably recognize these experts. No matter whom of the two you pick, if you follow his advice like a Lemming you will end like one. Whether it's Taubes' "Exercise will just make you hungry" (read more about the fallacy of this position) or Dr. Oz's mainstreamed diet advice.
Bottom line: I guess there is no bottom line as of yet. That does not change that the data from the study at hand was unquestionably news-worthy, though it certainly is but one of the billion pieces to the puzzle that holds the answer to the intrinsically flawed and useless question "Why do we get fat?" I mean, the question alone is telling you that people are delegating their responsibility for their physique and more importantly their health to others - to the government, to book authors, to bloggers like me, to gurus and to quacks.

So one answer to the question "Why do we get fat?" would be: "Since we pose the wrong questions, rely on the wrong answers and are too lazy and fainthearted to take our health into our own hands."

I guess that's not a popular answer, but there would not be a SuppVersity, if I did not truly believe that educating yourself and taking your health into your own hands, with the help, but not in blind obedience to the advice, counseling and experience of other, is was the answer to question that's of much greater importance to each of you, namely "How do I manage to stay healthy, happy and lean?"

References:
  • Austin GL, Ogden LG, Hill JO. Trends in carbohydrate, fat, and protein intakes and association with energy intake in normal-weight, overweight, and obese individuals: 1971-2006. Am J Clin Nutr. 2011 Apr;93(4):836-43. 
  • Ballard-Barbash R, Graubard I, Krebs-Smith SM, Schatzkin A, Thompson FE. Contribution of dieting to the inverse association between energy intake and body mass index. Eur J Clin Nutr. 1996 Feb;50(2):98-106.
  • Nielsen SJ, Popkin BM. Patterns and trends in food portion sizes, 1977-1998. JAMA. 2003 Jan 22-29;289(4):450-3.
  • Romieu I, Willett WC, Stampfer MJ, Colditz GA, Sampson L, Rosner B, Hennekens CH, Speizer FE. Energy intake and other determinants of relative weight. Am J Clin Nutr. 1988 Mar;47(3):406-12.
  • Yancy WS, Wang CC, Maciejewski ML. Trends in energy and macronutrient intakes by weight status over four decades. Public Health Nutr. 2013 Jan 16:1-10.