How much weight can you lose in a week?
When it comes to weight loss we all know the formula – get more active and eat less calories, and weight loss will be your reward. But is it as simple as that and can you lose too much weight for it to be healthy and sustainable?
Why might you need to lose weight?
If you’ve been advised by a medical professional that you’re overweight or obese this may put you at an increased risk of developing serious health problems, including heart disease and diabetes. Carrying extra weight has practical implications, too, because it puts extra pressure on joints and makes it harder to exercise. It also increases the likelihood of sleep disturbances including sleep apnoea.
If you’re overweight or obese, losing 5-10% of your body weight can bring numerous benefits – not only will you feel better and be able to move with more ease but you should experience improvements in blood sugar control, have less joint pain and lower your risk of chronic health conditions later in life.
What is healthy weight loss?
National guidelines recommend that, for gradual weight loss, a reduction in calorie intake or an increase in activity levels equivalent to 500-600kcal a day is needed. This may lead to a weekly weight loss of around 0.5kg (1lb). This may be an effective way to start your weight loss regime but it is usually only helpful for the first few months, after which hormonal changes may halt any further loss.
As research progresses we’re beginning to understand that the theory of ‘calories in and calories out’ is an oversimplification of the way our body uses energy. There are many other factors at play including the type of food we eat, how we prepare these foods, our own basal metabolic rate and even the type of bacteria that live in our gut.
If you start to experience a plateau in your weight loss it’s likely that you need to incorporate more activity into your day – studies report that optimum weight loss is achieved when calorie restriction is combined with moderate activity. Read our guide on the many health benefits of walking.
What is excessive weight loss?
A weekly loss in excess of 1kg (2lb) for a sustained period, is considered by most experts to be too much. However, you should bear in mind that during the initial weeks of any diet you’re likely to appear to lose more weight – this will actually be body fluids. When we cut calories, our body turns to our glycogen stores to make up the shortfall. Glycogen is stored in the body bound to water so as we burn glycogen we release more water making our weight loss appear greater. Once glycogen stores are largely depleted your weight loss will stabilise.
What are the dangers of losing weight too quickly?
While a special event or occasion may make it tempting to lose weight fast, it’s not recommended. Very low-calorie diets are likely to be low in important nutrients and adopting such a diet over a period of weeks may leave you short, resulting in conditions like anaemia. A restrictive diet can also lead to an imbalance in electrolytes – these natural salts and minerals play an important role in regulating the balance of our body fluids.
Losing weight too quickly is thought to be associated with a larger loss of lean body mass and a reduction in resting metabolic rate – the rate at which we burn calories. It may also put you at increased risk of nutritional deficiencies and more likely to develop gallstones. Adopting a restrictive diet is tough and the low level of calories may leave you feeling tired, mentally drained and irritable.
Sadly, most dieters regain half the weight they lose within a year, with nearly all dieters regaining their lost weight after three to five years. Slower, more steady weight loss appears to protect the weight you lose for the longer term and this steady pace allows you the time to establish healthier eating behaviours which are key to successful long-term weight control.
Is weight loss safe for everyone?
Pregnant and breastfeeding women, as well as diabetics on medication, should seek medical advice before embarking on a restricted eating programme. Furthermore, weight loss diets may be unsafe for teenagers and children, who are likely to miss out on crucial nutrients needed for growth, and they may also be at increased risk of developing unhealthy eating habits or harmful obsessions.
Although many of us want to be a perfect weight now, losing weight at a slow, steady pace, about 0.5kg (1lb) per week, is likely to be more sustainable and will put you at less risk of health issues. Most of us focus on following a diet but it’s actually after we lose the weight that we need to exercise more focus – this is key to keeping off the weight we’ve lost.
By making gradual dietary changes that become habits, we can build healthier behaviours which are more sustainable for the longer term. Combining this healthy weight loss with exercise is also more effective for maintaining muscle mass, protecting our metabolic advantage and for achieving cardiovascular benefits.
Please note, if you are considering any form of diet, please consult your GP first to ensure you can do so without risk to health.
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Kerry Torrens BSc. (Hons) PgCert MBANT is a Registered Nutritionist with a post graduate diploma in Personalised Nutrition & Nutritional Therapy. She is a member of the British Association for Nutrition and Lifestyle Medicine (BANT) and a member of the Guild of Food Writers. Over the last 15 years she has been a contributing author to a number of nutritional and cookery publications including BBC Good Food. Find her on Instagram at @kerry_torrens_nutrition_
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