Is it sensible to lose weight rapidly? How healthy is it? Will I be able to keep the weight off? These much debated questions are what make many people sceptic about rapid weight loss. But is it really that bad?
What is rapid weight loss?
In order to lose weight fast, you have to restrict your food intake or eat foods that are low in calories.
Rapid weight loss is defined as weight loss achieved through daily dietary intake of 800 kcal or less. Such a diet should however contain sufficient amounts of all essential nutrients.
Normally about 1.5kg-2.5kg of weight is lost per week by following a rapid weight loss diet. 
What do the critics say?
Rapid weight loss is widely criticized and in the opinion of most critics:
- Weight that is lost too fast, is regained very easily and quickly.
- Rapid weight loss diets do not work well in the long term.
- Personal health can be greatly impacted by rapid weight loss.
Studies have shown that these critics provided insufficient evidence to prove their assumptions. And that rapid weight loss: 
- Is not connected to rapid weight regain.
- Has benefits for long term weight maintenance.
- Can be beneficial for overall health.
Does rapid weight loss work?
To lose a considerable amount of weight in a short period of time is highly effective. The rate at which weight is lost has no effect on long term weight gain. The only difference between gradual and rapid weight loss is time. 
Rapid weight loss effects on the body
Rapid Weight loss has many benefits for physical and psychological health.
It has been proven that rapid weight loss does not affect physical strength and performance. A study was conducted during which the physical performance of athletes was tested after gradual and rapid weight loss procedures. The results showed that their physical performance was not hampered by rapid weight loss. 
Furthermore, weight loss from very low calorie diets have been linked to a reduction in C-reactive protein. This is a protein becomes elevated in the body when inflammation, which is a leading cause of heart disease, is present. Thus rapid weight loss has benefits for heart health. 
Rapid weight loss is also beneficial for psychological health. A study proved that athletes had a mental advantage and greater mental diversity after following a rapid weight loss program. 
So what’s the verdict?
Even though rapid weight loss is widely disputed, the truth is that this type of weight loss is can give you results in a short period of time and have lasting results on weight loss and health.
- Mustajoki P, Pekkarinen AT. Very low energy diets in the treatment of obesity. Obesity reviews. February 2001; vol. 2(1): 61–72.
- Volek JS, Westman EC. Very-low-carbohydrate weight-loss diets revisited. Cleve Clin J Med. November 2002; vol. 69(11): 849, 853, 856-858.
- Casazza K, Fontaine KR, Astrup A, Birch LL, Brown AW, Bohan Brown MM et al. Myths, Presumptions, and facts about obesity. New Engl J Med. January 2013: vol. 368: 446-454.
- Purcell K, Sumithran P, Prendergast LA, Bouniu CJ, Delbridge E, Proietto J. The effect of rate of weight loss on long-term weight management: a randomised controlled trial. The Lancet Diabetes & Endocrinology. December 2014; vol. 2(12): 954-962.
- Hemmingsson E, Johansson K, Eriksson J, Sundström J, Neovius M, Marcus C. Weight loss and dropout during a commercial weight-loss program including a very-low-calorie diet, a low-calorie diet, or restricted normal food: observational cohort study. Am J Clin Nutr. September 2012; vol. 96(5): 953-961.
- Fogelholm GM, Koskinen R, Laakso J, Rankinen T, Ruokonen I. Gradual and rapid weight loss: effects on nutrition and performance in male athletes. Med Sci Sports Exerc. 1993; vol. 25(3): 371-377.
- Heilbronn LK, Noakes M, Clifton PM. Energy restriction and weight Loss on very-low-fat diets reduce C-reactive protein concentrations in obese, healthy women. Arterioscler Thromb Vasc Biol. 2001; 21: 968-970.
- Pettersson S, Ekström MP, Berg CM .Practices of weight regulation among elite athletes in combat sports: a matter of mental advantage? J Athl Train. 2013 January-February; vol. 48(1): 99-108.