Crash Diets : New Evidence Suggests They May Be Effective, But Is This Accurate?


As a health and nutrition professional I am obligated to stay abreast of current information, whether I like what the research is saying or not. Naturally it doesn’t seem logical that the faddy nature of ‘crash dieting’ is better than gradual weight loss. The risk of newspapers posting the most recent finding (note I use the singular term ‘finding’) in dieting is that the lay public may read this and latch on to it, convinced that this is now the only way to go…well I can tell you that it’s NOT, but it's interesting all the same.

Yes, this study deserves to be considered, it was after all conducted by professional researchers and doctorates in their professional area. As well as this, the research was peer reviewed before it was accepted into the scientific journal meaning it comes with some validity. HOWEVER, this is just 1 study, and therefore does not change the overall consensus that a healthy balanced diet over time is the best way to lose weight. Before I go on any further, let’s look into the study, its validity, and the overall message behind the research:

What did the study show?

The study was performed in Australia and followed 200 obese adults who were incentivised to lose 12.5% of their bodyweight in 12 weeks, and for some, 36 weeks. Those are the facts, and I’ll go straight for the jugular here…immediately I can establish that this study isn’t representative of the general population based on the fact it was only conducted on obese individuals. So the study may well have shown that obese people were able to lose weight more readily when they crash dieted, but by no means is this necessarily transferrable to the general public!

The study also found that 8 out of 10 dieters managed to lose their target weight on the crash diet, whereas 50% of those on the steady diet were unable. However, I feel this overlooks the plethora of studies that demonstrate how steady weight loss is more sustainable than rapid weight loss, and how people who lose weight fast are more likely to regain the weight. This said, the lead Dietitian does qualify this by explaining that the people who lost weight rapidly (in this study) seemed to reach their target weight more consistently, and with a lower drop out. This is encouraging and understandable, humans like to see results, are enthused to continue when they see something working and are therefore less likely to drop out. What would be really encouraging was if there were several studies to this effect, but it’s an interesting start.

The people who crash dieted lost more weight in the short term, but it was interesting to see how the number of people who regained weight after the rapid weight loss diet was the same as those who lost weight from steady dieting. This tells us (at least in this study) that people who crash dieted lost more weight in the short, but didn’t gain any more than steady dieting in the long term.

Overall validity of the study

I feel the research findings are a little misleading in the sense that it implies the rate of fat loss in obese individuals is transferrable to the general public as a whole, but with this said the findings are interesting and well gathered. The validity of the study is largely evidenced by the quality of the journal it was published in (The Lancet) and is further validated by highly influential individuals including Professors of Oxford University and the likes of. Professor Susan Jebb of Oxford University states that ‘the study is important and well conducted. It shows that the common claim that rapid initial weight loss is followed by more rapid weight is false’. She goes on to say:

“This is important because it will enable professionals to recommend a broader range of treatment options so that people may be more likely to find the one that is best suited to their lifestyle.

“Interestingly, the rapid weight loss group were more likely to achieve their target weight loss and more likely to stick with the programme. These factors are both important to successful weight control.”

On the flip side of this, leading Dietitians and nutrition research experts explain that losing weight over 36 weeks (as was the case for the steady weight loss) didn’t really constitute ‘gradual’ or ‘steady’ weight loss. Therefore if the individuals had been given more time to lose the weight, so that it was steady weight loss in the truest meaning of the word, then the results and subsequent weight regain may have been different.

Concerns around very low calorie, rapid weight loss diets

Despite this useful piece of research, there is still concern around the safety of very low calorie diets in the sense that a particularly low calorie diet (something in the region of 800kcal) can result in vitamin and mineral deficiencies because the foods eaten to meet these calories do not deliver enough. It is therefore advised that people consume a multi- vitamin and mineral should they wish to consume a very low calorie diet. Gaynor Bussell, a Dietitian explains that rapid weight loss is great for motivation and sticking with a diet because results occur faster and more readily than steady weight loss diet. A number of hormonal shifts come into play when weight loss occurs over a short period of time, for example, hunger is often suppressed on very low calorie diets because of the release of ketones. However, ketones can make the blood pH reduce so that it is too acidic, this can place strain on ones kidneys. As a result of this lack of hunger, people will stop eating and therefore miss out on key vitamins and minerals! Gaynor states that a minimum of 1200kcals a day are usually needed in order to deliver all the vitamins and minerals needed to meet ones requirements.

There are risks when it comes to rapid weight loss, people may cut calories too fast and too dramatically in order to reach their target weight quicker. The overwhelming majority of research is still in support of steady weight loss, however this recent study is evidence that rapid weight loss may not be the devil we all initially thought it to be. If you ask me, the safest and most effective way to lose weight so that it stays lost, is to do it gradually over time, the risk of you missing out on nutrients is less whilst the chances of you rapidly regaining the weight you lost is reduced.



The Telegraph, (2014). Crash-dieting more effective than gradual weight loss, study suggests. Retrieved 20th October, 2014, from

Purcell K, Sumithran P, Prendergast LA, et al. The effect of rate of weight loss on long-term weight management: a randomised controlled trial. The Lancet Diabetes & Endocrinology. Published online October 16 2014





About the Author

Job Role Qualified Dietitian and Sports Nutritionist Qualifications BSc (Hons) Sports Science | BSc (Hons) Dietetics Tom has always participated in sport both recreationally and competitively which led to an unquenchable thirst for information on anything health, nutrition and fitness. After leaving school Tom went on to play for a football academy during which time he studied Sport and Exercise Science. From here he went on to study a BSc (Hons) Sport Science at UEA followed by his second BSc (Hons) degree, this time at the University of Hertfordshire studying Dietetics. Tom has worked in the fitness, educational and clinical nutrition industry starting out at David Lloyd Health and Leisure Clubs. He then went on to work as a Dietitian (RD) in the NHS, during which time he conducted clinics for healthy eating, weight loss and weight gain, as well as specialised consultations on Diabetes, IBS and Coeliac disease to name a few. He has vast amounts of experience at devising diet plans and supplement regimens, as well as working in the community with schools and competitive athletes. As Head Nutritionist and Supplement expert at Discount Supplements Tom is here to provide current and evidence based health and nutrition information to help you reach your health and fitness goals!
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