IMI Nutritionist Katia Demekhina discusses the dangers of crash diets and the safest way to achieve the optimal body weight.
Kim Kardashian lost 7kg in 3 weeks to fit into a dress for 15 minutes of fame. Is this extreme form of dieting the solution we’ve all been looking for?
A lot of people are trying to lose weight, particularly with the summer months approaching. If you’re overweight or obese, which 30% of adults in Hong Kong and 40% globally are, then losing weight is a good thing. It’s not just the thin-ideal images in the media that contribute to weight dissatisfaction. Excess weight often goes hand in hand with health risks like diabetes, high blood pressure, heart disease and more.
But “quick fix” diets, as tempting as they may sound, are not the answer. Crash diets are risky – they can cause a host of health issues. Also, weight loss should be about achieving actual health goals and not about going to the extremes to fit into a particular piece of clothing (only for the weight to return).
What are extreme diets and what are the consequences, whether positive or negative, on one’s body composition and health? We’ll discuss this and more here.
Pitfalls of crash dieting
Crash diets are typically diets that provide less than 800 calories a day. While over the short-term such diets may help you see a decrease in the number on the scales, would they improve your health outcomes and happiness in the long term? This question has been frequently raised in research as people look for an answer to shedding stubborn weight.
You may remember “The Biggest Loser” contest in the US, where obese or overweight contestants compete to win a cash prize by losing the most weight. In 2016, a group of researchers checked in with 14 out of 16 participants of this contest six years after the end of the weight-loss competition. Their findings? The majority of participants regained over 40kg of weight lost and their resting metabolic rate (which is the rate at which our bodies burn calories at rest) stayed over 500kcal/day below baseline despite weight regain1. In other words, the extreme weight loss was accompanied by a slowdown in metabolism. And the rate of metabolism did not recover even after the individuals stopped their extreme diets, making it impossible to keep the weight off. Astonishing, right?
“The Biggest Loser” contestants are not unique in their inability to maintain weight loss. When researchers analysed 29 weight loss studies with over a thousand participants they found that more than half of the lost weight was regained within two years, and by year five more than 80% of the lost weight was regained2.
You may be wondering, ‘why is it so difficult to lose weight and keep it off?’ Research sheds some light on this.
Decreases in resting metabolic rate are a well-known consequence of weight loss3. When you drastically reduce calories, even if you need to lose weight, your body thinks you’re starving. Starvation is considered a big stressor for the body as it can hinder survival. As a protective mechanism, the body slows down the metabolism to help you conserve energy and hang on to the body fat. In addition, calorie-restrictive diets may cause your body to break down the muscle for energy and fuel. Not only do you wave goodbye to your shapely form, but a loss in muscle mass can also slow down your metabolism. Muscle is one of the most metabolically active tissues in the body and your muscle mass is a key determinant of your resting metabolic rate4. Other tissues like bone can also suffer as the body breaks down all tissues to generate energy. One study noted a significant loss of total hip bone mineral density in older women following extreme diets5.
A well-known risk of crash diets is gallstones formation, with 12-25% of individuals on very low calory diet developing cholelithiasis6. This risk is three-times greater in extreme dieters than moderate ones7. Increased risk of gallstone formation during very low calorie diets could be a consequence of the rapid weight loss associated with such diets and/or an inadequate fat content of the diet6.
And it is not just fat that could be nutritionally deficient in crash diets. Starvation diets tend to be nutritionally unbalanced and deprive the body of many essential nutrients. We get our nutrition (protein, fats, vitamins, minerals, and more) from the food we eat. Our bodies can’t produce some of these nutrients (we call these “essential”) and we must get them in minimum amounts from our diet regularly to assure good health. When you dramatically reduce what you eat, it can be very hard to meet your nutritional requirements. While most of us have adequate nutrient stores to go for short periods of time without all our essential nutrients, we can’t do this for long. Nutrient deficiencies may lead to short- and long-term poor physical and mental health.
Crash diets can make you feel tired, irritable, lacking in concentration and unable to function properly. This could be a consequence of low blood sugar, as well as toxins being released into the circulation. Environmental pollutants and other toxins are stored in our fat cells. During weight loss, fat breaks down and toxins are discharged into the bloodstream. Not only are these toxins released in large quantities during rapid weight loss, but crash diets also do not provide the body with the nutrients needed to keep the liver working hard to detoxify these. We end up feeling miserable.
Fast vs. slow weight loss
There may be a time and a place for extreme low-calorie approaches to weight loss. Such drastic diets have been used successfully in obese individuals with a BMI of at least 30 kg/m2 – a group at increased risk of cardiovascular morbidity and mortality. However, even in such cases where one has a lot of weight to lose, careful medical supervision during the rapid weight loss is advised due to the risks we discussed earlier 6. And even then, such an extreme dietary approach poses the risk of malnutrition and is often followed by a large level of weight regain subsequent to the end of the diet8. This raises doubts as to whether such crash dietary approach is the solution even when it’s deemed necessary to lose a lot of weight.
Is there a better way to lose weight and keep it off? An analysis of close to 400 dieters has revealed that even among obese individuals, while the magnitude of weight loss is similar, gradual weight loss promotes a greater reduction in fat mass and body fat percentage9. So, while it may be tempting to follow a “quick fix” diet, a more favourable body composition can be achieved with a slow weight loss approach. Specifically, slower weight loss is associated with a greater reduction in waist circumference, hip circumference, and fat mass
4. Furthermore, during similar weight loss, rapid weight loss results in a much greater loss of muscle mass than gradual weight loss10. As a decrease in muscle tissue during weight loss could hinder the success of your weight loss efforts, preservation of muscle mass accompanied by fat lass loss is the ideal outcome following dietary weight loss. This could be one of the reasons why slow weight loss also preserves the resting metabolic rate compared to rapid weight loss9, making it easier to maintain the weight.
So slow weight loss results in a much better body composition long-term. What about the impact of different weight loss approaches on a person’s health? When it comes to improvements to metabolic health markers (such as waist circumference and blood pressure), it is the absolute weight loss sustained, rather than the speed of weight loss that makes the biggest difference11.
Tips for achieving optimal body weight
A lot of thought should go into your weight loss approach. It’s more than just jumping into the latest fad or a celebrity crash diet.
While it may seem tempting to engage in dramatic and rapid weight loss, the foundation for losing weight and keeping it off is to eat a nutritious and well-balanced diet. And when I say diet, I don’t mean a “diet” which has a specific start and an end date, meaning you only change what and how you eat during this specific period and then return to your old habits. I mean creating a sustainable lifestyle that will contribute to your long-term health goals, help maintain weight and, most importantly, make you feel good about yourself.
While there isn’t a one-size-fits-all approach, there are some foundations that everyone needs to consider to achieve a healthy sustainable weight loss. These include:
- Consuming adequate protein
- Cutting back on sugar and simple carbs
- Eating healthy fats such as fatty fish, avocado, olive oil and nuts
- Prioritising sleep
- Managing stress
- Engaging in an appropriate level and kind of exercise
And remember, that although slow and steady weight loss doesn’t sound as promising, it’s the best way to honour your body. It’s also way more effective in helping you achieve your health and weight goals, keep the weight off in the long run and develop a healthy relationship with food.
How can a nutritional therapist help with weight loss?
Each and every one of us is unique. A qualified nutritional therapist can help design a personalised approach to weight loss taking into account your health history, goals and circumstances. Rather than taking a prescriptive approach, we negotiate a program that works within your preferences and constraints, empowering you to make knowledgeable choices and making it effortless for you to implement the changes. Furthermore, by uncovering the root causes of excess weight we can target specific biological mechanisms that may influence your body’s propensity to accumulate body fat or affect hunger and satiety.
Making long-term changes can take effort and dedication. This is why failure to achieve and maintain substantial weight loss over the long term is often attributed to behavioural fatigue in adhering to the prescribed diet and lifestyle changes 6. A significant part of weight loss and management may involve restructuring the environment that promotes unhealthy choices. It also involves changing everyday habits that you may have acquired over the years. While it is tempting to think that willpower is the key to successful weight loss, self-control is similar to a muscle12; and just as a muscle gets tired from exertion, so can self-control. This is why our good intentions tend to fail when we are tired or stressed. With the help of neuro-linguistic programming techniques and psychological tools, we can help rewire the brain and build new habits, strengthen motivation by aligning it with personal values and goals, and restructure the environment to take away the need to rely on the willpower and make the changes effortless.
 Fothergill, E. et al. Persistent metabolic adaptation 6 years after “The Biggest Loser” competition: Persistent Metabolic Adaptation. Obesity 24, 1612–1619 (2016).
 Anderson, J. W., Konz, E. C., Frederich, R. C. & Wood, C. L. Long-term weight-loss maintenance: a meta-analysis of US studies. Am. J. Clin. Nutr. 74, 579–584 (2001).
 Müller, M. J., Enderle, J. & Bosy-Westphal, A. Changes in Energy Expenditure with Weight Gain and Weight Loss in Humans. Curr. Obes. Rep. 5, 413–423 (2016).
 Ashtary-Larky, D. et al. Waist Circumference to Height Ratio: Better Correlation with Fat Mass Than Other Anthropometric Indices During Dietary Weight Loss in Different Rates. Int. J. Endocrinol. Metab. 16, e55023 (2018).
 Seimon, R. V. et al. Effect of Weight Loss via Severe vs Moderate Energy Restriction on Lean Mass and Body Composition Among Postmenopausal Women With Obesity: The TEMPO Diet Randomized Clinical Trial. JAMA Netw. Open 2, e1913733 (2019).
 Tsai, A. G. & Wadden, T. A. The Evolution of Very-Low-Calorie Diets: An Update and Meta-analysis. Obesity 14, 1283–1293 (2006).
 Johansson, K., Sundström, J., Marcus, C., Hemmingsson, E. & Neovius, M. Risk of symptomatic gallstones and cholecystectomy after a very-low-calorie diet or low-calorie diet in a commercial weight loss program: 1-year matched cohort study. Int. J. Obes. 2005 38, 279–284 (2014).
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 Ashtary-Larky, D. et al. Effects of gradual weight loss v. rapid weight loss on body composition and RMR: a systematic review and meta-analysis. Br. J. Nutr. 124, 1121–1132 (2020).
 Vink, R. G., Roumans, N. J. T., Arkenbosch, L. A. J., Mariman, E. C. M. & van Baak, M. A. The effect of rate of weight loss on long-term weight regain in adults with overweight and obesity. Obesity 24, 321–327 (2016).
 Kuk, J. L., Christensen, R. A. G. & Wharton, S. Absolute Weight Loss, and Not Weight Loss Rate, Is Associated with Better Improvements in Metabolic Health. J. Obes. 2019, 1–6 (2019).
 Baumeister, R. F., Vohs, K. D. & Tice, D. M. The Strength Model of Self-Control. Curr. Dir. Psychol. Sci. 16, 351–355 (2007).