Lots of people seek to achieve sustainable weight and improve their metabolic health. You don’t have to look far to find the many dietary approaches purported to lead to weight loss. From books, television and the internet, everywhere is awash with quasi-scientific diets and amazing ‘miracle cure’ products spouting outlandish claims of lightning-fast weight loss.
Although desirable, losing weight too quickly can be dangerous for your health. This article will take a closer delve into what might be considered a healthy rate of weight loss, alongside the risks that quickly losing weight brings.
What is a healthy rate of weight loss?
It might be tempting to try and lose as much weight as quickly as possible, yet the expert consensus is that 1-2 pounds per week is key for sustainable weight loss.
You may find you lose a greater amount of weight in the first few weeks of your weight loss journey. However, this is nothing to worry about, with this initial change likely to a drop in water weight – particularly if you are lowering the number of carbs in your diet.
Diets that encourage faster weight loss even after rapidly losing water weight are unlikely to be sustainable in the long term and can cause some negative health consequences.
Health risks of losing weight too fast
Weight loss results from having a negative energy balance, where we have burnt more calories than we have consumed. Drastically cutting down the calories we eat rather than having a moderate calorie deficit has been linked with multiple health risks.
Whether we are seeking to gain weight or not, a well-balanced diet is essential for good health. Obtaining enough essential nutrients like vitamins and minerals, protein and fat from the food we eat helps our bodies to function as they should.
Cutting down on our food intake too much means we are unlikely to reach our nutrient requirements. Not eating an adequate amount of nutritious food increases our risk of nutrient deficiencies, leading to health problems such as an impaired immune system and wound healing, reduced fertility and inactivity of the muscles.
Not all weight loss is equal. When we are seeking to improve our metabolic health, we should be aiming to lose weight from our body fat stores while sustaining and increasing our muscle mass.
Unfortunately, the readings on most scales do not distinguish between fat and muscle loss.
Previous studies have found that losing weight too fast can lead to more muscle loss in comparison with slower weight loss.  With less muscle, we are not as insulin sensitive, which can culminate in greater weight gain due to a reduced metabolic rate.
Sustainable and slower weight loss, combined with exercise and a sufficient protein intake, can help prevent muscle loss when losing weight.
Diet myths have often perpetuated the idea that weight loss is as simple as cutting down calories to lose weight. However, this does not take into consideration the ways the human body can adapt to weight loss.
Restricting our calorie intake by too much or for too long causes our metabolism to slow down – which means we burn fewer calories than we did previously. As discussed above, this is partly down to muscle loss, which is more significant when weight loss is rapid.
However, our bodies have also evolved to preserve our body fat stores. While this was useful when food was scarce, it makes weight loss harder when someone is hoping to improve their metabolic health.
When faced with weight loss, the body reacts by burning less energy, allocating what remains to our most essential tissues. This reallocation can result in drops in body temperature, alongside low energy levels, which reduce our drive to burn calories through movement. After a while, the body restores its energy balance, and a further calorie reduction is required for continued weight loss.
One study investigated the metabolic rates of participants who had previously competed on “The Biggest Loser” – a show where the aim was to shed the most amount of weight over a brief period of time.  Contestants lost 56kg on average while taking part on the show, although this weight loss was due to a severely restricted calorie intake and excessive exercise.
When the researchers revisited the participants six years later, they found the individuals had regained an average of 41kg and now burned 700 calories fewer each day than before their rapid weight loss.
The results of The Biggest Loser follow-up study demonstrate the damage to your metabolism that extreme rapid weight loss strategies can do, even making it harder to maintain healthy weight loss afterwards.
Research studies have shown that an approximate 80% of people who lose a significant amount of their body weight often regain it within the space of five years.  This proves that although short-term weight loss is achievable, the real challenge is to maintain it in the long run.
Maintaining weight loss requires a dietary approach that can be incorporated into your lifestyle. Diets that are very low in calories – inducing rapid weight loss – are just not sustainable over a long period of time. Restrictive approaches to weight loss typically trigger changes in appetite hormones which make us feel hungrier, causing us to overcompensate on what we eat and eventually resulting in weight regain. 
Focusing on long-term behaviour change is a better approach to maintaining weight loss. While changing unhealthy habits is not something that happens overnight, it helps create a productive mindset that will lead to sustainable weight loss.
As tempting as quick weight loss strategies appear, research has consistently proven that severely restricting our calorie intake carries the risk of nutrient deficiencies, muscle loss, and a slower metabolism.
A sustainable weight loss goal is a recommended 1-2 pounds per week.
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