Episode 64 – Are Dietary Guidelines Contributing to Obesity?

Key Topics Covered

We will be mostly focusing on the Australian dietary guidelines to keep it simple – but there will be some mention of the American dietary guidelines, since it is an important part of the narrative. 

This is obviously quite a complex topic, so we will try to cover as much as we can. 

How Have Obesity Rates Changed Over Time?   

  • Definition of obesity is BMI 30kg/m^2 – obviously there are flaws in BMI – but that’s the metric that is used. 
  • Based on that definition close to 30% of Australian adults fit the criteria for obesity. ~36% of Americans do, for comparison. 
  • In 1995, 19.1% of Australian adults were classified as obese. So there has been significant increase since then.  

How Do the Guidelines Fit In With This Timeline  

  • The first US dietary guidelines were released in 1980. The first Australian ones were in 1982. 
  • Discuss the chart below – very slow increase in overweight/obesity rates prior to 1980 – then a steep increase from there. Overweight/obesity was at ~47% of the population prior to that point – whereas by 2007 it was at ~73%.  
  • Charts like this look compelling – but did other aspects change around that time? Is it easier or more appealing to be more sedentary? Is there more access to higher calorie food?  
  • Overweight/0besitY rates in U.S. 
75 
65 
E 55 
50 
45 
1960 
Government issues dietary guidelines. 1980 
1965 
1970 
1975 
1980 
1985 
1990 
1995 
2000 2005 2010 
Source: CDC data

Criticisms of the Guidelines 

  • A major criticism of the guidelines is that they have typically been “low-fat” focused
    • which has supposedly led to increase in carbohydrate, in particular in the form of refined carbohydrates and sugar.  
    • It’s worth noting that current Australian guidelines don’t actually have a limit on total fat. Instead it currently just says to limit saturated fat.  
    • We have a separate acceptable macronutrient distribution range of 20-35% of total calories that is “government advice” but not technically part of the guidelines.  
  • The high amount of dairy 2.5-4 serves per day 
    • Mostly reduced fat options – stated in the guidelines 
    • Doesn’t have to be dairy – just calcium rich options  
    • But even if this was all dairy it could be as little as – 1 cup skim milk in your morning coffee, a yoghurt for morning tea and a small amount of cheese on lunch  
  • The high amount of wholegrains 4-6 serves per day 
    • 1 serve is equal to 1 slice bread 
    • So again this is a really large amount – it could be – ½ cup cooked porridge for breakfast, a sandwich for lunch and 1 cup cooked pasta for dinner (that’s 5 serves) 
    • The criticism probably comes from the link people often make between carbs and weight gain
      • But it is not usually wholegrains that are the issue – it’s often refined grains high in added sugar and fats 

Does Anybody Actually Follow the Guidelines Though?  

  • The average person does not actually know the guidelines well. To be fair they are pretty boring – and the PDF is literally 226 pages long. 
  • There are a lot of recommendations like “limit intake of foods containing added salt” or “limit intakes of foods containing added sugar” that are clearly not followed at a population level. 
  • If we go with the standard “eat 2 serves of fruit and 5 serves of vegetables recommendation” only 6% of Australians meet that recommendation. So if only 6% of Australians meet that mark, what percentage come close to doing anything resembling the dietary guidelines? 
  • Dietary guidelines similar between countries, but obesity rates are significantly different e.g. South Korea has an obesity rate of 1.6% (or 3-4% depending on the stats) and Qatar is at 41.4% 

Defence of the Guidelines / Additional Context That Is Necessary   

  • Who are the guidelines designed for
    • Healthy individuals without medical conditions and/or in situations requiring individualised advice.  
  • The guidelines include the physical activity recommendations of aiming for at least 30 minutes of exercise on most, if not all days. For those not meeting this amount, the guidelines become less relevant, because nutrition needs are different if you are more sedentary. 
  • The guidelines have always recommended limiting added sugar. Acting as if the guidelines recommendation to limit fat to <30% of total calories (when they first appeared) was the equivalent of encouraging increasing sugar intake is really cherry picking which parts of the guidelines you want to listen to.  
  • The guidelines have always encouraged wholegrain and mostly unprocessed foods, not large amounts of refined carbohydrates.  
  • In Australia >1/3 of calories come from “discretionary foods” which are meant to be limited to a minimum according to the guidelines.
    • If we do that AND have a lot of wholegrains + dairy etc, then it will lead to a higher than desired calorie intake.  
    • The numbers recommended in the guidelines are made under the assumption that discretionary foods/drinks/alcohol are limited. 

A Balanced Perspective 

  • Does it make sense that our guidelines are designed for people who are healthy, fit and exercising 30+ minutes almost every day, when that description does not really fit the majority of our population? I don’t really have a solution here – but a lot of criticism stems from people assessing the quality of the guidelines for situations it’s not really designed for
  • The higher carbohydrate intake fits in with an active lifestyle, but does not fit as well with a sedentary lifestyle. Likewise it often does not fit as well with certain medical conditions such as diabetes, if done without context.  
  • One point worth acknowledging is that consumer trends did switch in the 80s towards wanting lower fat products, which lead to many companies reducing the fat content of their products and often increasing the sugar content in the process. People claim that this was due to guidelines. But companies switched due consumer demands. Did consumers demand this because of the guidelines? Or for other reasons? 
  • In the guidelines, they actually mention that they are still relevant for people who are overweight, so long as they don’t have medical conditions. Personally I would likely adjust things a bit for those who were looking to lose weight. During a fat loss phase, I’d almost always be aiming for lower carbohydrates than the dietary guidelines (not necessarily low carb), to leave room for enough protein for muscle retention. 
  • Most people who argue that the guidelines are harmful, are also trying to build the case for a low carb diet. If the argument is about low carb vs low fat diets for weight management – this topic has been studied extensively both in controlled situations and real world situations showing that both options work equally well.  

Summary 

  • The guidelines have had very little to do with the increased rates of obesity.  
  • While I do not actively promote the guidelines, I also think that people following the advice in the guidelines across the board, not just 1-2 aspects like aiming to reduce fat intake, would likely reduce obesity rates rather than increase it.  
  • Obesity is multifactorial, but there are a lot of other factors that have a much stronger impact in why obesity rates have increased over time.  
     

Related Links/ Resources

Studies Mentioned

Related Bog Posts