How to lose weight correctly, Risks of losing weight too fast

How to lose weight correctly
Table of Contents

Is it safe to lose weight quickly? Watch out, you could be hurting your health!

Risks of losing weight too fast? Overweight people are often overwhelmed by their health and body aesthetics. That's an unquestionable fact.

Some admit it, others not so much and there are those who learn to accept themselves and live with it, but all of them, at some point, have been worried about their high weight.

Facing this scenario is not an easy task. For this reason, the best possible support and information is required about the damage that obesity has on an individual's health and how we can manage it.

The fundamental pillars in the treatment of overweight are diet and exercise.

There are diets that, combined with an intense training program, offer the possibility of losing a large amount of weight in a short period of time.

Some of them have shown significant efficiency, with weight reduction and body mass index (BMI) reaching up to 30% over a period of a few weeks or months.

While these results are extraordinarily successful, we must ask ourselves Is losing so much weight in such a short time healthy? Let's see what science has to say about that.

Extreme diets

extreme diets, risks of losing weight too quickly

In November 2018, a group of Indian researchers led by Dr. Joshi Shipa and Dr. Mohan Viswanathan presented a study evaluating the advantages and disadvantages of some popular diets that offer extreme weight loss in a short time.

In this paper published by The Indian Journal of Medical Research, it is noted that obesity is not just a public health problem in the developed world.

They also indicate that many developing countries have alarming numbers of overweight and diabetes in their populations, which - and this is due to their backwardness - are not properly addressed and generate high rates of cardiovascular morbidity and mortality.

The authors of this study classify extreme diets into two types:

  • Low-carbohydrate/high-fat.
  • Low-fat/high-carbohydrate.

Having both distinct effects on the organism as explained below.

Low-carbohydrate/high-fat diets

These diets are characterized by having less than 100 grams a day of carbohydrates, based mainly on fat (>60%).

They're an example of these: 

Actual weight loss is due to caloric restriction, which can reach 1,000 kilo-calories per day.

Although these diets show a significant decrease in blood glucose, insulinemia, and lipid levels in the blood, lack of vegetables and fruits can lead to loss of bone mass and increased uric acid.

This diet also promotes oxidative stress and pro-inflammatory pathways.

Low-fat/high-carbohydrate diets

This type of diet is defined by its low amount of fat, ranging between 11% and 19%, although in some cases it may be less than 10%.

Emphasis is placed on consuming complex carbohydrates and plenty of fiber.

While low-density lipoprotein (LDL or bad cholesterol) levels may be decreased by these diets, this effect is not sustained.

In fact, after a while an increase in triglyceride values is observed.

Another negative element in these diets is taste.

Fats provide a lot of taste when cooking and although it may seem like a minor factor, it is difficult to stick to a tasteless diet.

A large percentage of the long-term failure of this type of food is associated with its poor taste.

The researchers conclude that while people who are truly willing to lose weight may try these types of diets, none seem to work in the long run.

Evidence of this is the ease with which these diets appear and disappear from the nutritional landscape of society.

Losing weight is not the same as keeping it off and achieving this without an effective exercise program is impossible.

What about those who "need" to lose weight quickly?

There are groups of people who, for one reason or another, need to lose large amounts of weight in a short period of time.

The best example of this is the patient who will undergo bariatric surgery due to morbid obesity.

Many athletes, especially in contact sports, also tend to lose weight violently in order to participate in their ideal category.

This type of people who need to lose weight too quickly have to have an Endocrinology doctor's follow-up.

Bariatric patients.

obese woman

A clinical trial carried out in the unit of bariatric and metabolic surgery at the University Hospital of Sao Paulo (Clinics Sao Paulo, 2019) analyzed the metabolic behavior of 120 patients selected for bariatric surgery and submitted to a diet of 600 kilo-calories daily (20% proteins, 20% fats and 60% carbohydrates) for one week.

On average, patients lost 5% of their body weight in 7 days, which is favorable for surgical and anesthetic management, but there was also a decrease in muscle mass.

This latter finding is worrisome for overweight people because it means they are not only losing fat but also muscle as a result of these diets.

Preserving muscles is vital when sudden weight loss is expected after surgery.


losing weight too fast, athletes

The department of molecular and cellular medicine, part of the German Institute for Cardiovascular Research and Sports Medicine, published a paper about the immediate consequences of rapid weight loss in taekwondo fighters and whether or not this affects their performance (PLOS One, 2018).

The conclusions reached by the German researchers were conclusive: there is no improvement in the performance of the athletes after 3 days of intense diet and exercise.

In addition, they detected important alterations in the blood, causing a decrease in the transport of oxygen and problems in coagulation.

These effects are believed to be sequels of oxidative stress and activation of the inflammatory cascade associated with exercise and diet.

The organism feels hurt and acts that way.

Pro-inflammatory effect of rapid weight loss

inflammatory effect of rapid weight loss

One of the most feared consequences of rapid weight loss is the alteration of the pro-inflammatory cascade, but what does this mean?

Inflammation is a normal response of the body to any aggression..

Many times we associate inflammation only with the increase in volume or swelling that appears after a blow, but it is much more complex.

Inflammation also occurs inside the body and depends on many factors and substances produced in the body.

Thus, infections and autoimmune diseases also cause inflammation.

Research conducted by a group of New York scientists and published in 2017 by the Journal of the Endocrine Society analyzes the issue of obesity-associated inflammation in post-menopausal women.

For decades it has been known that obesity alone induces the production of pro-inflammatory substances capable of maintaining a state of constant alteration in the body, behaving practically like an infection or a politraumatism.

Losing weight has also been shown to help these substances lower their blood levels and return to normal.

This does not happen with rapid weight loss.

In fact, the main difference found between patients who lose weight after bariatric surgery (gradually) and those who do so by consuming very-low-calorie diets (quickly) was the level of some proinflammatory substances in the blood.

Patients who lose weight progressively have lower levels while those who lose weight quickly maintain high values.

The body's inability to adapt to its new weight seems to be the cause of this phenomenon.

Rapid weight loss is also thought to behave differently about visceral fat than it does about subcutaneous fat.

Weight loss and dementia

In recent years there has been much discussion about the role of obesity in the risk of dementia or Alzheimer's disease. Since The Lancet Diabetes and Endocrinology published in 2015 that famous study in which British scientists claimed that having a high body mass index (BMI) protected against Alzheimer's, much more research has been done.

It is definitely not clear whether or not a lower BMI is associated with cognitive impairment but weight loss is a common feature of Alzheimer's disease and often occurs before the onset of clinical symptoms, suggesting that a low BMI may be a clinical feature of the pathological process of Alzheimer's disease rather than a risk factor.

Dr. Susan Bell and her team at the Vanderbilt University Alzheimer's and Memory Center in Nashville published an interesting article in The Journal of Nutrition, Health and Aging (2017) in which they evaluate the protective role of obesity in older patients at risk for Alzheimer's, and one of the most striking discoveries was that those people when they lost weight quickly - whether through diet, exercise or some other disease - lost the defense that overweight offered against dementia and other cognitive pathologies.

This phenomenon did not occur with those individuals who maintained a high BMI or who lowered little.

What can rapid weight loss cause?. Rapid weight loss vs. slow weight loss

It is not easy for an overweight person or his collaborators to decide which technique to apply to lose weight.

Anyone would like to lose weight quickly, but they would also like this result to be long-term.

Faced with this dilemma, a team of Iranian researchers conducted a study comparing the metabolic and body composition effects of rapid weight loss diets compared to others for gradual weight loss.

This work was published in 2017 by The International Journal of Endocrinology and Metabolism and studied more than 40 overweight people, divided into two groups: the first lost about 5% of its weight in 5 weeks and the second also 5% of its weight, but in 15 weeks.

While the goal was achieved in both groups, not only was a weight taken into account.

Hip and waist circumference, amount of total body water, fat mass, and basal metabolic rate were assessed.

The results showed that the rapid weight loss group only outperformed the "slow" group in glycemic control parameters, in everything else, including body measurements, people who lost their planned weight in 15 weeks did better.

On the other hand, long-term results remained most successful in the slow weight loss group.


happy slim woman

The exhaustive review of the literature about weight loss only shows that there is no perfect formula that offers you at the same time the speed, security, and durability of the results.

What seems clearer is that fast alternatives can be very effective, but at the same time dangerous.

Only in exceptional situations should they be chosen instead of those that offer gradual weight loss.

The immediacy of achievements may seem attractive but it is not always positive.

Whatever the decision, you should always have professional support.

Losing weight is an arduous task and the percentage of failures and abandonment of diets and physical activity is very high and this often happens because we do not have the right people by our side.

Obesity is not healthy and must be treated, but it must be done well.

Joshi S y Mohan V (2018). Pros & cons of some popular extreme weight-loss diets. The Indian journal of medical research, 148(5), 642–647.
Serafim MP, Santo MA, Gadducci AV, Scabim VM, Cecconello I y de Cleva R (2019). Very low-calorie diet in candidates for bariatric surgery: change in body composition during rapid weight loss. Clinics (Sao Paulo, Brazil), 74.
Yang WH, Heine O y Grau, M (2018). Rapid weight reduction does not impair athletic performance of Taekwondo athletes - A pilot study. PloS one, 13(4).
Bell SP, Liu D, Samuels LR y colaboradores (2017). Late-Life Body Mass Index, Rapid Weight Loss, Apolipoprotein E ε4 and the Risk of Cognitive Decline and Incident Dementia. The journal of nutrition, health & aging, 21(10), 1259–1267.
Alemán JO, Iyengar NM, Walker JM and collaborators (2017). Effects of Rapid Weight Loss on Systemic and Adipose Tissue Inflammation and Metabolism in Obese Postmenopausal Women. Journal of the Endocrine Society, 1(6), 625–637.
Ashtary-Larky D, Ghanavati M, Lamuchi-Deli N and collaborators (2017). Rapid Weight Loss vs. Slow Weight Loss: Which is More Effective on Body Composition and Metabolic Risk Factors? International journal of endocrinology and metabolism, 15(3).