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Low-Carb Diets and False Hope Syndrome

Unrealistic expectations and the adoption of extreme low-carb diets.

Key points

  • Trendy low-carb diets promise quick, easy weight loss, but research shows that regaining weight lost is a particular concern for low-carb diets.
  • People on high-protein, low-carb diets often see increased weight loss within the first week but this is largely due to water loss from the body.
  • The "false hope syndrome" is characterized by unrealistic expectations of self-change and is strongly exploited by the diet industry.

Trendy low-carb diets promise easy and quick weight loss, limited restriction of portions, favorite foods, and, most importantly, a greater sense of well-being.

Unfortunately, as with all the other diets, most people regain the weight lost. However, regaining weight after weight loss is a particular concern for low-carb diets. In a study with prolonged follow-up, weight gain after initial weight loss at six years was greatest with low-carbohydrate diets (4.1 kg regained) and less with those on low-fat and Mediterranean diets (2.7 and 1.4 kg regained, respectively).

In most cases, people have little knowledge of the reasons for regaining weight and often become prey to the low-carb fashion extreme and rigid diets that promise quick and easy weight loss.

A Brief History of Low-Carb Diets

Low-carb diets have a long and cyclical history of popularity. Two thousand years ago, the Greek Olympians ate a lot of meat and few vegetables to improve their athletic performance.

Dr. William Harvey, in 1600, recommended in patients who needed to increase diuresis a diet that prohibited sweets and starches and allowed the ad libitum consumption of meat.

However, Dr. William Banting, with the publication of the "Letter on Corpulence, Addressed to the Public" in 1863, was the first doctor to recommend a low-carb diet specifically to lose weight. The diet consisted of four meals a day and included meat, vegetables, fruits, dry wine, and recommended the avoidance of sugar, starches, beer, milk, and butter. This paper, printed until 2007 and still available online, became popular and was used as a model for modern high-protein, low-carb diets that regained popularity in the late '60s and early '70s with the Atkins, Stillman, and Scarsdale diets.

Criticism of low-carb diets by some important medical associations, such as the American Medical Association has limited the spread of these diets. However, the increase in obesity and the prevalence of insulin resistance has gradually seen its resurgence in Western countries. Current low-carb diets, although they have used different names (e.g., Sugar Busters Diet, Carbohydrate Addicts Diet, Protein Power Diet, Zone Diet, Paleo Diet, Plank Diet, Dunkan Diet, Ketogenic Diet), are all variations of the original Atkins diet.

The common claim of these diets is that carbohydrate restriction allows losing weight by eating as much food as one wants. This statement has certain truth because, in some people, the intake of high amounts of protein seems to suppress appetite. A similar effect has been associated with ketosis resulting from carbohydrate restriction. Furthermore, carbohydrate limitation can help eliminate some popular foods that are often consumed in excesses, such as bread, cereals, soft drinks, French fries, and pizza — a strategy that allows creating a daily energy deficit of about 500 kcal, as observed in people who follow the Atkins diet.

Why Do Low-Carb Diets Initially Make You Lose More Weight?

It is widely known that a reduction in caloric intake of about 500 kcal per day produces a weight loss of approximately 0.5 kilograms per week. However, high-protein and low-carb diets may produce a two- to three-kilogram weight loss in the first week. This greater weight loss is not due, as some incorrectly affirm, to a miraculous metabolic switch resulting in greater fat burning but is the mere consequence of an increase in diuresis induced by the diet. In fact, when limiting carbohydrate intake, two simultaneous metabolic processes occur that reduce the body's water content.

The first process is the mobilization of glycogen reserves in the liver and muscles. Each gram of glycogen is mobilized with about two grams of water. It has been calculated that about 100 grams of glycogen are deposited in the liver and about 400 grams in the muscle. This means that the loss of glycogen reserves causes a weight loss of about one kilogram. This change, which is appreciated by those who try to lose weight, is often associated with a decrease in the sense of swelling.

The second process exploited by ketogenetic diets is the production of ketone bodies by the catabolism of the diet and endogenous fats. The kidney filters ketone bodies as non-absorbable anions and their presence in the fluids of the renal tubules increase the distal release of sodium and water loss with the urine.

A study that compared a mixed diet of 800 kcal with a ketogenic of diet 800 kcal found that weight loss after ten days was 4.6 kilograms with the ketogenic diet and 2.8 kilograms with the mixed diet. However, the assessment of nitrogen-energy balance documented that the difference in weight loss was due entirely to the greater loss of water achieved by the ketogenic diet than the mixed diet.

Long-Term Weight Loss Is Affected by Caloric Restriction, Not by the Composition of the Diet

The diuretic effect of the low-carb diet is limited to the first week. Subsequently, weight loss follows the laws of energy balance and not of diet composition.

The so-called ''carbohydrate-insulin model of obesity'' has been, in fact, falsified by basic research. The model postulates that diets rich in carbohydrates are particularly fattening because they increase insulin secretion and accumulate fat in adipose tissue, removing it from oxidation by metabolically active tissues. This altered partition of fats would result in a state of ''cellular hunger'' that produces an adaptive increase in hunger and suppression of energy expenditure. The carbohydrate-insulin model implies that a low-carb, high-fat diet should reverse these processes and result in weight loss without effort.

However, the mechanisms proposed by the carbohydrate-insulin model have been disproved by studies performed in metabolic chambers. Indeed, studies comparing isocaloric diets, which vary in the ratio of carbohydrates to fats, tend to confirm the saying "a calorie is a calorie" in the production of fat loss.

The absence of differences in weight loss between low- and high-carbohydrate diets has also been confirmed by a meta-analysis review of 48 trials (7286 patients with overweight/obesity) that evaluated the effects of 13 popular diets with a 24-week follow-up. A significant weight loss was observed with any type of diet low in fat or carbohydrates, and the differences in the amount of weight loss between the diets were minimal.

In conclusion, the current evidence suggests that there are no advantages in reducing carbohydrates to the amount of weight lost. Moreover, low-carb diets are associated with potential adverse effects (e.g., dehydration, constipation, headache, kidney stones, cardiac arrhythmias, hypercholesterolemia, osteoporosis, impaired cognitive function, micronutrient deficiency, etc). In contrast, some traditional eating patterns, such as Mediterranean diets, have been shown to have important health benefits and to reduce mortality from cardiovascular diseases.

The False Hope Syndrome

Despite the above facts, the popularity of ketogenic diets and other extreme, rigid diets has increased in recent years. This is probably mainly due to the "false hope syndrome," as defined by Janet Polivy, professor emeritus of psychology at the University of Toronto Mississauga, which may characterize unrealistic expectations of self-change of people who diet and is strongly exploited by the diet industry.

The false hope is based, as affirmed by Polivy, on the dysfunctional belief that "change is easily achieved and that it will produce exaggerated benefits."

In the field of dieting, studies have observed that people seem to behave paradoxically by persisting in repeated attempts to lose weight with extreme and rigid diets, despite previous failures. Initial weight loss often provides powerful positive reinforcement, although it is then followed by failure because feelings of control and optimism often accompany it. In addition, unrealistic expectations regarding ease, speed, the likely degree of weight loss, and the supposed benefits obtained from achieving the desired weight loss goals tend to overwhelm the knowledge derived from previous failures. Indeed, failure to lose weight is often the consequence of adopting an extreme and rigid diet, which obviously cannot be maintained long term.

The false hope of those who follow the extreme and rigid diets promoted by the diet industry, such as trendy low-carb diets, reflects the desire of people to believe that they can get what they want. False hopes develop, in fact, because people want to believe them.


Schwarzfuchs, D., Golan, R., & Shai, I. (2012). Four-year follow-up after two-year dietary interventions. New England Journal of Medicine, 367(14), 1373-1374.

Hall, K. D. (2017). A review of the carbohydrate-insulin model of obesity. European Journal of Clinical Nutrition, 71(3), 323-326. doi:10.1038/ejcn.2016.260

Polivy, J. (2001). The false hope syndrome: unrealistic expectations of self-change. International Journal of Obesity and Related Metabolic Disorders, 25 Suppl 1, S80-84. doi:10.1038/sj.ijo.0801705

Johnston, B. C., Kanters, S., Bandayrel, K., Wu, P., Naji, F., Siemieniuk, R. A., . . . Mills, E. J. (2014). Comparison of weight loss among named diet programs in overweight and obese adults. JAMA, 312(9). doi:10.1001/jama.2014.10397