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The Fast Track Trial Pilot Study Results

By Louise Adams

An article in The Age newspaper about the Fast Track controversially stated that:

"While the trial is the first of its kind, Professor Baur said it had come off the back of a successful pilot program in which 25 teenagers followed a similar model and saw benefits in their cholesterol, blood pressure, liver and heart function."

The Fast Track research team have a history of being overly optimistic in their research. Is it possible that once again, the conclusions don’t match the data? Let’s take a deeper look at this newly published study, and see what actually happened in their 'successful pilot program'.

45 teenagers were approached, and 30 were ‘recruited’ from a hospital based childhood obesity clinic. The teens were aged 12 to 17, there were 25 girls and 5 boys. All of the teens were supposed to have a BMI of 30 or more. In fact, they ranged from a BMI of 27.7 to 52.4, so at least one was well below the weight threshold.

The experiment ran for 6 months and was based at Westmead hospital in Sydney, under a dietitian. There were no psychologists or eating disorder specialists involved. For the first 12 weeks all of the kids were placed on Optifast (shakes) and allowed just 600-700 calories a day for 3 days of the week. The rest of the week the kids were told to follow ‘healthy eating guidelines’. 

After 12 weeks teens were ‘invited’ to either keep starving for 3 days a week, or they could change to starving for 2 or 1 day a week, or they could swap to a ‘continuous prescribed healthy eating plan’ for the next 3 months.

7 of the kids didn’t make it past the 8 week mark. These tended to be ‘heavier’ kids. We don’t know what happened to them after that. 2 more dropped out before the experiment ended, so overall just 21 teens finished the whole 6 months.

The kids were given a Fitbit, but were not given any instructions about physical activity. Mysteriously, the pilot paper never discusses the fitbit results. 

Main Results

So what happened to these kids - did they lose a lot of weight and improve their health? Here’s a summary of the results:

  • Most kids lost @3.5kg over the first 12 weeks

  • By 6 months, they had regained @1.4kgs, so an overall difference of @2kg after 6 months of starving, and they are highly likely to keep regaining

  • No major health improvements were found

  • 1 ‘super responder’ lost a lot of weight, which skewed the data

  • ⅓ of the kids dropped out before the study ended

  • Dietary restraint scores increased, which indicates increased eating disorder risk.

Let’s take a closer look at the results:


  • In the paper, it’s surprisingly difficult to see exactly what weight changes occurred. This is because of the way the data was reported. Weight change was primarily reported as ‘percentage point change in BMI 95th%ile’, a very confusing statistic which stops everyday people from figuring out what the actual average change in weight was. A researcher can tell you something is statistically ‘significant’ even if it’s not that meaningful in real life.

  • Luckily, the lead author presented her data at a conference where she did talk about the average kg weight loss for 19 of the 21 study completers.

  • At this conference, she reported that after 12 weeks of intermittent starvation, the kids had lost on average 3.5kg.

  • But by 26 weeks, these changes were not maintained; the teens had regained 1.4kg, so in total after 6 months of regular starvation, they were @2kg less than when they started, and they are likely to keep regaining.​

  • The published paper includes a graph (above) which shows what happened to each individual teenager - on the graph, each diamond represents one kid. We can see that 3 of the kids either stayed the same or gained weight even after 12 weeks of semi starvation. We can also see that most of the teens changed their % in BMI95th%ile by around 5-10% - this is not a huge change and it translates to very small changes in actual kg weight.

  • We can see that at the 6 month point, more of the kids are actually heavier than they were before the starvation diet - 4 of them are now above the starting line. This reflects our bodies’ metabolic resistance to weight loss.

  • We can also see one kid who has really lost a lot of weight. In weight loss research we call this a ‘super responder’. Clearly, this kids’ weight loss is very different to everyone else’s, and because this one person has responded in this way, their data changed the whole outcome of the experiment. In the conference presentation, weight loss between 12 and 26 weeks was ‘not sustained’, because the super responder was not included. But here in the published paper, thanks to one kid who may very well have developed an eating disorder, we now have ‘sustained weight loss results’.

  • The published pilot study completely ignores the weight regain that happened to the majority of the kids in the study. It’s not discussed AT ALL, a trend which is unfortunately very common in weight scienceresearch. 

Growth, Impact on Menstruation & Metabolism

  • Worryingly, the results show a significant reduction in height between 12 and 26 weeks. This was not discussed in the paper. This means that the teens' growth cycle is being interrupted. If a growing body is not getting adequate nutrition, the body will stop growing in order to compensate.

  • Any impact of starvation on the teens’ menstrual cycle was not investigated. Given that 25 of the 30 were girls, this is staggering.

  • Metabolic impact of starvation on the teenagers’ growing bodies was not measured or discussed in the paper.

Health Markers

  • 28 of the 30 kids were reported to be ‘insulin resistant’ at the outset of the experiment. This was exactly the same after 6 months of semi starvation.

  • Measures of cardiometabolic risk including cholesterol, blood pressure, and insulin resistance did not change after 6 months of intermittent starvation. Small changes in plasma triglycerides were reported, but these were in the normal range to begin with. A small increase in fasting plasma glucose occurred at 6 months, but overall no changes in insulin resistance occurred. 

  • Expensive and complicated vascular structure and function (heart) measures were taken, of 9 vascular measures only one was significantly changed by 6 months - arterial wall thickness. Measures of these factors were not taken for all of the completers.

  • The comments made to The Age newspaper regarding the effectiveness of the Fast Track pilot are not true. The teenagers in the pilot study did not see "benefits in their cholesterol, blood pressure, liver and heart function". At best, one aspect of a secondary marker of heart function improved at 6 months, but the majority of bio-markers were unchanged.

Psychological Impact

  • Dietary restraint - a measure which can indicate disordered eating and presence of an eating disorder - significantly increased by 26 weeks. These scores were elevated to start with and became even higher as the starvation diet progressed.

  • Although the paper reported ‘improvements’ in emotional eating and eating for external reasons, these scores were not unusual to begin with, therefore any reductions do not reflect a real life improvement, they are likely just reflecting the fact that the teens were eating less overall.

  • Of 7 measured areas of quality of life, only 2 showed improvement by the end of the 6 months. Interestingly, the results showed that improvements in quality of life were more likely to happen for those kids who did manage to maintain their weight loss at 6 months, the ones who didn’t maintain their weight loss were worse off. Given that we know that all of these kids will continue to regain weight, it seems likely that their quality of life measures will worsen. However, the researchers will not follow them up long enough to find out.


  • We know that 9 kids dropped out and only 21 finished the whole 6 months. At 6 months, 5 of the completers had stopped doing the intermittent starvation days altogether. This means that nearly half of the group who started the diet had either dropped out or stopped doing the strict diet by 6 months. The paper did not provide a reason as to why the 5 ‘successful’ kids decided to stop doing the fasting. The paper instead talks about how many of the kids felt that they found the diet ‘easy and enjoyable’. This contradicts the actual data.


  • In spite of objectively poor results, the authors merrily conclude that “IER is an effective dietary intervention which can lead to reductions in BMI and cardiometabolic risk.”

  • This is a highly optimistic conclusion which does not reflect what actually happened to the teenagers, a frequent pattern for the Fast Track researchers. 

  • The Fast Track researchers are not informing parents or teenagers of the likelihood of small weight losses followed by weight regain. This should be communicated clearly to parents and teens given the evidence from this pilot.

  • Parents and teens are also not being told of the increased risk of eating disorder markers, such as dietary restraint. This should be communicated clearly to parents and teens given the evidence from this pilot.

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