‘Pie hole’, colloquial for one’s mouth, is believed to have evolved in the USA in the 1980s from the British expression ‘cake hole’ (coined in the mid 20th century). Pie hole refers to a mouth, as in: Shut your pie hole or, in this case: Put less in your pie hole.

Wednesday, August 7, 2013

Cutting Carbs: A Cockamamie Idea

It's been in the news and under the spotlight for many years now:  Low carbohydrate diets. This topic doesn't require much of an introduction. So let's jump right in, what does the science say about low carbohydrate diets?

First off, a little history. Robert Atkins began promoting the low carbohydrate approach to weight loss in the 1970s, based on a research paper written in the late 1950s (that's a mighty old study). The diet was revamped in 2002 with the release of his second book on the topic.

Next up, what is a carbohydrate? Carbohydrates, or 'carbs' are one of the large nutrient classes. When digested, carbs break down into sugars that are used by cells, tissues, muscles and organs. Interestingly, the brain can utilise ketones (byproduct of fat breakdown) for energy, but preferentially and primarily uses glucose (a sugar) to function. Perhaps the 'carbs are evil' mantra is a result of carb cutter's suffering from declining brain activity. See figs 1 & 2 for types of carbs and number of daily serves recommended.
Figure 1: What a serve of carbohydrate looks like and number of serves recommended for adults (adapted from the Australian Guide to Healthy Eating 2013)
Figure 2: Examples of a serve of carbohydrates (adapted from the Australian Guide to Healthy Eating 2013)
A recent meta analysis (combination and analysis of independent studies) found short term weight loss benefits for low carb dieters... But (and there's always a but) no long term cardiac (heart) benefits were found. In fact, those on long term low carb diets had an increased risk of death. Hypothesised reasons for this:
  • Low carb diets are generally higher in protein
  •  Low carb diets are generally low in fiber
    • Many fruits are restricted, as are whole grains (oats, wheat, rice, pasta, legumes)
    • These are both extremely good sources of fiber - evidence shows high fiber diets are protective against many cancers, heart disease and high cholesterol
In the short term, favourable effects of a low carb diet are seen with regard to weight loss and improved blood sugar control.

Let's think about that: It stands to reason, because poor blood sugar control in someone who eats excessive carbohydrates causes insulin resistance - where the body must produce more than normal amounts of the regulatory hormone that controls blood sugar - insulin. If you decrease the carbs being eaten, of course blood sugar levels will improve... Duh. That's like saying, I will continue to be drunk if I continue drinking alcohol vs sobering up if I drink less.

The take home messages and tips:
  • Research does not support long term low carb diets
    • A better method is changing your eating habits long term, rather than a 'diet' (something you start and stop)
  • Putting whole grain sources of carbohydrates in your pie hole is beneficial for your health
    • They provide fiber, slow releasing energy and reduce the risk of cancers, type II diabetes and heart disease
    • Eating carbohydrate foods (Figs 1 & 2) ensures not overeating protein to compensate for removing/restricting a whole food group

    For more information about daily serves of grains and how grains contribute fiber to your diet, see:


    1. The PubMed article you cite for why meat causes cancer and why high fiber diets are protective seems very problematic to me in this context. The more unhealthy group in the study was not on a low carb diet. They ate meat, grains and sugars. High sugar diets have been shown in many studies to contribute to pancreatic cancer. They also cause inflammation and many be a huge contributing factor in conditions such as heart disease.
      There has never been a conclusive study that eating cholesterol or saturated fat causes heart disease. On the other hand, cholesterol and saturated fat are vital parts of the human diet.
      Here are a few studies that are food for thought in this realm: http://ajcn.nutrition.org/content/early/2010/01/13/ajcn.2009.27725.abstract

      1. The poor diet in the pubmed article did include refined sugars and wasn't low carb, however this still supports a poor quality diet increases cancer risk compared to a high quality diet. You're right that research points to high sugar diets being linked to all sorts of nasty problems - not arguing that at all.

        Re cholesterol and sat fat: It's rare that anything is ever 'conclusive', there are always outliers or study designs that may show a different association. However, the consensus is that high sat fat/high cholesterol diets do play a role in disease development like atherosclerosis, CVD, stroke, etc. Usually this is because people who eat diets high in chol/sat fat generally don't eat many fruits/vegetables/whole grains. These together, create the perfect storm for disease pathogenesis.

        Thanks for your comment.