Changes in food cravings during Low-calorie and Very-low-calorie diets

C K. Martin, P M O´Neil, L Pawlow

Obesity Vol 14 No. January 1, 2006

The study included adult participants at the Medical University of South Carolina Weight Management Center. Participants first carried out a food craving inventory (FCI), after which they were divided into 2 different weight loss programs, 39 with a 1200-kcal intake and 59 with an 800-kcal intake. The programs involved meetings each week with a focus on CBT and diet and exercise modifications. All participants attended group sessions, but 8 participants in the 800-kcal group and 2 participants in the 1200-kcal group also had individual sessions. FCI was measured continually during the study via self-reporting.

Craving can be defined as an intense longing to eat a specific food or type of food that is difficult to resist. Craving differs from hunger in that only a specific food or type of food will reduce the desire, while hunger can be alleviated by any type of food. Studies show that cravings are common, and occur in 56-97% of the population and about 2-4 times per week.

Cravings are believed to contribute to our eating behaviors, which also include overeating. Studies show that 80-85% of all episodes of craving result in people eating the food that they craved. Studies also show that cravings correlate with BMI in type 2 diabetics and that craving high-fat foods is associated with obesity. One theory is that cravings arise from food restriction and that food cravings would increase as calorie intake decreases.

An earlier study of two groups of type 2 diabetics, one of which followed an LCD (in this case defined as 1000-1500 kcal) regimen and the other VLCD (400-500 kcal) for 20 weeks showed that the incidence of craving decreased in both groups. No correlation was seen between amount of weight loss and degree of reduction in craving.

The primary purpose of this study was to investigate changes in craving in two different weight loss programs. One program, here referred to as LCD, is a low-calorie diet that provides 1200 kcal per day, and the other program with supplementation of diet and meal replacements is here referred to as VLCD and provides 800 kcal, though in some cases up to 1000 kcal per day. (The definition of a low-calorie diet (LCD) according to EU/EC directives and the National Food Administration, however, is between 800-1200 kcal, which is why in this study a very low calorie diet (VLCD) is also classified as LCD).

The focus of the study was to investigate general craving or cravings for specific types of food (sweet, fat, carbohydrates and starchy foods, as well as greasy fast food). It was expected that general cravings would decrease while following a diet, especially for the 800-kcal group. A secondary purpose was to investigate the incidence of craving during the 800-kcal diet and after reintroduction of food. Yet another purpose was to assess the relationship between weight loss and changes in cravings during treatment.

The weight loss program with the low-calorie diet (LCD) continued for 20 weeks with a diet plan of at least 1200 kcal per day. The VLCD program continued for 12 weeks with 800 kcal per day. The first 12 weeks in both groups were compared because most participants on LCD change their diets after 12 weeks.

The VLCD program consisted of 3 phases. Phase 1 lasted for 12 weeks (liquid diet replacement) at 800 kcal per day. Participants had the option to replace one portion of liquid diet replacement per day with 2 bars. They also had the option of adding 1-2 bars in addition to the 800 kcal, for a total of 1000 kcal per day. 

Phase 2 (stepwise reintroduction of food) lasted for at least 6 weeks and a maximum of 12 weeks. Reintroduction with limited food choices was increased during week 6 until a final calorie intake of between 1200-1400 kcal per day was achieved.

Phase 3 was a 12-week stabilization phase on a low-calorie diet. This phase was not included in the study. 

The results of the study show that incidence of craving decreases with calorie restriction. The results showed a significantly lower incidence of cravings in the 800-kcal group compared with the 1200-kcal group among all measured variables (general cravings, sweet, fat, carbohydrate and starchy foods, as well as greasy fast food) from baseline to week 12. All incidence of craving decreased significantly in the 800-kcal group by week 6 and did not change afterwards, even after reintroduction of food. Changes in cravings were not related to weight loss.

Cravings do not increase with the use of low-calorie food with 1200 kcal or the use of diet and meal replacement providing at least 800 kcal.

The authors of the study discussed the possibility that the greater reduction in cravings in the 800-kcal group may have several explanations. First, the 800 kcal diet offers fewer varieties of food choices compared with the low-calorie food diet. A greater variety of foods could lead to a larger intake. Nor was any correlation seen between cravings and variation in tastes. Since the 800-kcal diet consisted of sweet beverages and bars, it was expected that only cravings for sweets would decrease, but the results showed that cravings for other types of food also decreased. 

A second reason for reduced cravings could be that hunger decreased in the individuals who received the 800-kcal diet, because food intake was restricted. A third reason could be that diet and meal replacements are less appetizing than the food in the 1200-kcal diet. At the same time, the authors did not feel that these reasons explain why cravings remained lower after the reintroduction of meals with food in the group that received the 800-kcal diet, since the participants continued to lose weight, although at a slower pace. The authors believe that lower weight and calorie restriction may be contributing factors to the continued decrease in cravings. 

Contrary to what was previously believed, these results show there is little reason to believe that the craving for food would increase with weight loss diets. Instead, the results from this study suggest that calorie restriction causes a decrease in cravings for various foods.

http://onlinelibrary.wiley.com/doi/10.1038/oby.2006.14/abstract