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ISSA, International Sports Sciences Association, Certified Personal Trainer, ISSAonline, Nutrition, Fat weight loss, fast weight regain, Short and Long-Term Effects of Losing Weight Too Fast

Short and Long-Term Effects of Losing Weight Too Fast

Reading Time: 5 minutes 30 seconds


DATE: 2022-08-17

“Lose 10 pounds in 10 days.” “Drop a belt size by the end of the week.” We’ve all seen these types of claims made by companies that sell weight loss products. Sure, if given the choice between fast weight loss and slow weight loss, most of us would pick the former. But this approach doesn’t come without costs.

Here we talk about the short and long-term effects of losing weight fast. We also provide strategies for getting to a healthy weight by losing at a more moderate pace. Before we get into both, we must first identify what losing weight too fast means. 

What Does Rapid Weight Loss Mean?

The National Library of Medicine defines rapid weight loss as losing more than two pounds per week for several weeks. Typically, rapid weight loss occurs from greatly reducing your calorie intake. If you look at almost any fad diet, you will see that most are incredibly low in calories.

Some people refer to this as going on a “crash diet.” They eat fewer calories with the intent of quick weight loss. While calorie restriction is often needed to create the deficit required for fat loss, going too far can cause you to lose weight much too fast. 

If you’re not careful, this can lead to short and long-term consequences. That’s why an extreme diet should not be followed without the supervision of a healthcare provider. (This type of diet is typically only used for people who are obese and also have severe health issues, such as diabetes and high blood pressure.)

Short-Term Effects of Losing Weight Too Quickly

If you’ve ever tried to lose weight as fast as possible, you may have experienced gastrointestinal issues. Both constipation and diarrhea can occur with fast weight loss. You might also struggle with nausea and fatigue.

Additionally, if it is fat loss that you’re after, a lower number on the scale may fool you into thinking that this is what you’re achieving from day one. In actuality, when first reducing your calories, what you typically lose is water weight. Why does this occur? 

Once you restrict your calories, your body taps into its glycogen stores for energy. This causes water to be released, resulting in a lower body weight. 

Another potential short-term consequence of quick weight loss is gout. Gout is a form of arthritis that often appears in the big toe and can be extremely painful. One study found that gout attacks tend to occur after bariatric surgery.

Other research connects sudden weight loss with an increased risk of gallstones. Gallstones are hard bile deposits that form in the gallbladder. If they travel, they can create a blockage. This can cause pain in the abdominal area. It can also lead to the development of gallbladder or liver disease.

Long-Term Impact of Too Fast Weight Loss

One of the most common long-term impacts of rapid weight loss is actually weight gain. Case in point: research indicates that after two years, less than half of people have sustained their lost weight. After five years, this drops to only one in five.

It’s easy to become mesmerized by TV shows that involve extreme weight loss and think we can do the same. Participants follow a low calorie diet and increase their physical activity to see who can lose the most weight. What we don’t see is that, for many, the weight loss is only temporary. 

One study noted assessed 16 participants on The Biggest Loser. They lost a mean of 58.3 kg (128.5 lbs) during the competition. However, after six years, around 41 kg (90.4 lbs) had been regained. Additionally, those who were able to maintain a greater weight loss over time also had greater metabolic slowing. So, their metabolism never rebounded after they lost weight.

Sticking to a very low calorie diet long-term can also lead to nutritional deficiencies. Your body needs certain nutrients for optimal function. If your diet is so limited that you can’t get all the nutrients in, you can become deficient in the ones that are lacking. This can lead to numerous other issues. 

For example, research has linked deficiencies in iron, copper, and zinc with hair loss. Deficiencies can also lead to poorer gut health. Gut health is important for the brain while also helping to protect against chronic disease. 

So, the effects of too quick weight loss are many and can change depending on what your diet looks like and how long you stick to this type of plan.

How to Achieve Healthy Weight Loss Instead

Most experts agree that if you want to lose weight, it’s healthiest to lose 1 to 2 pounds per week. This requires employing sustainable weight loss strategies consistent with a healthy lifestyle. Here are a few to consider:

  • Eat enough calories to meet your nutritional needs. If you or your client are not sure what these needs are, working with a nutritionist can help. Certain people have different nutritional requirements. They can change when pregnant or breastfeeding, for instance. They also change based on the stage of life, with some varying quite drastically based on whether the person is a teen, adult, or older adult.

  • Consume foods from each food group. One common theme among quick weight loss diets is that many omit entire categories of food. This is how deficiencies can start to form. Your diet should include carbs, protein, and fat. The key is to choose healthy versions of each. For instance, sources of healthy fat include avocado, olive oil, nuts, and seeds. Whole grains and fruit are healthy carbs while lean meats, fish, and eggs are each a source of healthy protein.

  • Choose natural over processed foods. Some diet plans consist primarily of pre-packaged or processed foods. This means that they contain other substances that might not be good for your health—even if they are within the dietary guidelines. Natural food sources are best.

  • Develop healthy eating habits. Do you tend to eat while standing at the cupboard or refrigerator? Are you usually the first one done with your meal? Not taking the time to sit down and enjoy your food slowly can keep your body from recognizing when you’ve had enough. Making small changes to eating habits such as these can help with weight loss.

  • Avoid fad or crash diets. Remember that these diet types are intended to be short-term. What happens when you go off them? Weight gain sets in. That’s why you’re better off creating a healthy lifestyle. You want to make changes to your diet that you can stick with for the long haul.

If you try all these things and don’t get results, make an appointment with your healthcare provider. It’s possible that something else is going on that may be limiting your ability to lose weight. 

You should also work with your healthcare provider if losing weight fast might offer more benefits than harm. If you are having trouble controlling your blood sugar, for instance, getting some extra weight off may help improve this control. 

Your provider may refer you to a nutritionist, who can work with you to create a diet plan that is suitable for you based on your condition and issues. 

From Weight Loss to Weight Management

Losing weight is only part of the journey. Once the weight is off, you must work to maintain the loss. This can be a challenge for many clients. 

Reinforcing that this is a lifestyle change can help. A diet is not something they can go “on” and “off.” Instead, it’s a way of eating that they follow for the rest of their lives.

Also work with them to let go of the fast weight loss mentality. Explain the negative short and long-term effects of taking this route. Let them know that, in the end, it is slower weight loss that provides the best results.

If you want to help your clients avoid weight regain, you can do this as a Certified Weight Management Specialist. This ISSA course discusses the myths and facts surrounding weight loss. It also provides strategies proven to help people keep weight off for good.

Featured Course

ISSA | Weight Management Specialist

As an ISSA Weight Management Specialist, you will be able to coach your clients with empathy and develop the skills to support them through their transformation.


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Stokes, C., & Lammert, F. (2021). Excess Body Weight and Gallstone Disease. Visceral Medicine, 37(4), 254-260. https://doi.org/10.1159/000516418

Hall, K. D., & Kahan, S. (2018). Maintenance of Lost Weight and Long-Term Management of Obesity. The Medical clinics of North America, 102(1), 183–197. https://doi.org/10.1016/j.mcna.2017.08.012

Fothergill, E., Guo, J., Howard, L., Kerns, J. C., Knuth, N. D., Brychta, R., Chen, K. Y., Skarulis, M. C., Walter, M., Walter, P. J., & Hall, K. D. (2016). Persistent metabolic adaptation 6 years after "The Biggest Loser" competition. Obesity (Silver Spring, Md.), 24(8), 1612–1619. https://doi.org/10.1002/oby.21538

Gowda, D., Premalatha, V., & Imtiyaz, D. B. (2017). Prevalence of Nutritional Deficiencies in Hair Loss among Indian Participants: Results of a Cross-sectional Study. International journal of trichology, 9(3), 101–104. https://doi.org/10.4103/ijt.ijt_48_16

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