1 October 2018


Overweight and obesity is a global phenomenon, with the World Health Organisation estimating in 2016, that 1,900 million adults and 380 million children have a body mass index (BMI) greater than 25 kg/m2. The causes are multifaceted and complex. In 2007, the Foresight Programme of the UK Government Office for Science published an obesity system map, developed through a multi-stakeholder process.

Obesity system map

This qualitative, conceptual model has 108 variables, some of which are measurable (eg, the ambient temperature of the indoor environment), and others that are more difficult to quantify (eg, desire to differentiate food offerings). The relationships between the variables are illustrated with more than 300 solid or dashed lines to indicate positive and negative influences. All the variables are interconnected, some with large numbers of inputs and others with large numbers of outputs. The connections give rise to feedback loops with as few as two variables (eg, a affects b which in turn affects a) or involving as many as 16 variables.

At the core of the map is “energy balance” (energy intake versus energy expenditure). 

The highest quality (Level 1) scientific evidence from randomised controlled trials in humans shows quite clearly that in the long-term (more than 2 years), the macronutrient composition (ie, fat, carbohydrate or protein) of the diet doesn’t matter – with respect to body weight, it’s total energy intake (kilojoules/calories) that ultimately counts. Despite this, most purveyors of popular diets continue to focus on single nutrients or ingredients as the cause of all our current lifestyle-related ailments, and most state of course that all you need to do to solve the problem is to avoid them. If only it was that simple …

We have a really good recent example of the lack of success of the one-nutrient-at-a-time approach – the vast variety of low fat diets contrived in the final quarter of the 20th century. Low fat diets (in contrast to traditional low-fat eating patterns as enjoyed by certain ethnic groups for hundreds of years) did not deliver the improvements in health that were expected by their original proponents.

Present day narrative suggests that in an academic showdown spanning both sides of the Atlantic in the 1960s and 70s, “anti-fat” scientist Dr Ancel Keys defeated “anti-sugar” scientist Dr John Yudkin, and the low-fat message was enshrined in Dietary Guidelines worldwide, paving the way for low-fat variants of all of our favourite foods for the next quarter of a century. In the mean-time we all gained more weight and developed type 2 diabetes. Again, if only it was that simple …

Not everyone agreed with Keys hypotheses, and as characteristic of scientific research, academic debate continued. Mindful of this, the very first edition of the Dietary Guidelines for Americans published in 1980 included a range of practical advice to help people choose a healthful pattern of eating. There was a chapter on how to “Avoid too much fat, saturated fat, and cholesterol” and also one on how to “Avoid too much sugar”, thus addressing both Keys’ and Yudkin’s concerns. Dietary Guidelines from 1980 onwards have always included practical advice on reducing saturated fat and added sugars. The problem is, the average person didn’t know about the Dietary Guidelines as they were a government publication in a pre-internet world. Needless to say, they would not have been on the best seller list in the local bookstore back in 1980. Even today few people have actually read them despite their being freely available over the internet.

In the 1970s and 80s, low-fat diet books by Nathan Pritikin in the USA and Ross Horne in Australia (an engineer and a pilot respectively) made the best seller lists. They had both experienced dramatic health improvements when they started consuming a low-fat diet. There were many other similar titles as the publishing industry caught and rode the wave. Devout followers of the various low-fat gurus sought low-fat foods in their local supermarkets and food industry caught on, producing low-fat versions of all of our favourite foods, often replacing the fat with dietary fibres (eg, gums), maltodextrins, starches, added sugars and refined proteins. The rest, as they say, is history …

Sadly, history has a bad habit of repeating itself. With respect to fad diets, the cycle appears to last around 50 years. Here’s a snapshot of the past 50 years.
  • High fat, low carbohydrate diets were fashionable in the early 1970s thanks to Dr Atkins’ and his Diet Revolution: The High Calorie Way to Stay Thin Forever 
  • Low fat, high carbohydrate diets came into fashion in the early 1980s, thanks to Nathan Pritikin’s The Pritikin Promise: 28 Days to a Longer Healthier Life and Ross Horne’s The New Health Revolution, and stayed with us for around 20 years 
  • Low carbohydrate, high protein diet variants came back in vogue in early 1999 with the release of Dr Atkins New Diet Revolution, and The CSIRO Total Wellbeing Diet in 2006. 
  • Low sugar diets became popular in the mid-noughties, and low carbohydrate (starches and sugars) diets have been popular in more recent years. Indeed, extremely low carbohydrate/high fat diets are now in vogue, with ketogenic diets rapidly gaining in popularity – last popular back in 1971 ... 
When you break it down and do the math it’s pretty simple – there are 3 macronutrients:

50 years/3 macronutrients = new focus for fad diets every 15–20 years. 

So it’s protein’s turn for the hit list next. Veganism or test-tube meat anyone?

Let’s break the cycle. Diets don’t work. Instead, opt for what we know works for long-term health and wellbeing.
  • Enjoy a healthful pattern of eating that suits your cultural, family and personal food preferences and budget 
  • Be as physically active as you can every day 
  • Find ways to deal with stress, and 
  • Get a good night’s sleep. Eight hours. 
Read more: 

Dr Alan Barclay  
Alan Barclay, PhD is a consultant dietitian and chef (Cert III). He worked for Diabetes Australia (NSW) from 1998–2014 . He is author/co-author of more than 30 scientific publications, and author/co-author of  The good Carbs Cookbook (Murdoch Books), Reversing Diabetes (Murdoch Books), The Low GI Diet: Managing Type 2 Diabetes (Hachette Australia) and The Ultimate Guide to Sugars and Sweeteners (The Experiment, New York).

Contact: You can follow him on Twitter or check out his website.