Prevalence of obesity in industrialized countries has been continuously rising for more than three decades.[1], [2] Elevated disease risks linked to overweight and obesity have led authorities to consider this epidemic a major public health challenge.[3], [4] Moreover, social pressure to adhere to a thin body image ideal exposes those not meeting it to consequences encompassing both personal and professional challenges.[5], [6] Both medical concerns and this social pressure for thinness drive more and more people to dieting.[7]–[9] In the USA in 2005–2006, 36.9% of men and 57% of women had been on some type of a weight loss diet in the year preceding the report, which represented a 10% increase for women compared to 5 years earlier.[9], [10]

In this context, the weight-loss market has been growing rapidly in response to the demand and now includes a number of commercial diet plans/programs, self-help books written by “celebrity-status” physicians, mobile diet applications and websites, and word-of-mouth marketing. In 2011, the weight-loss market was estimated to be worth $60 billion in the USA[11], and almost 3 billion € in France.[12] Very few commercial diet plans have accepted to be evaluated using scientific rationale and methodology[13]–[15], instead relying on anecdotal evidence to establish their effectiveness.[16] Aside from well-defined commercial offers or medical advice, individuals can also self-impose dietary restrictions.[17] In addition, official dietary recommendations and guidelines issued by the respective authorities can serve as alternate and reliable sources of information for individuals wishing to achieve a balanced diet in order to lose weight.[18], [19] Finally, in specific clinical settings, nutritional medical counselling is recommended.

In spite of the large number and diversity of the available weight-loss strategies, little is known about their actual use in the population or the perception of each strategy by the consumers.[16]

Irrespective of the type of weight-loss diet used, weight regain is common, often reaching or even exceeding the initial weight.[20]–[22] A major determinant of weight loss and weight maintenance is adherence to the diet,[23] which is dependent on the perception of and the conditions under which the diet is followed.[24], [25] However, the literature on these aspects of weight-loss practices is scarce. To our knowledge, no study has yet described in detail the various weight-loss strategies in a large sample of the general population, or has documented perceptions of weight-loss diets.

Our objectives were to investigate perceptions of weight-loss strategies in a large sample of the general population in order to identify the best perceived strategy. We hypothesized that weight-loss strategies would differ by gender, and we therefore conducted separate analyses for men and women.[9], [26], [27]

Between April 1, 2012 and October 12, 2012, 48 435 subjects had completed the questionnaire about dieting strategies. Among them, 12 628 subjects (26.7%) had followed at least one weight-loss diet in the previous three years (detailed information in the Figure S1). Compared to non-dieters having completed the questionnaire, dieters were more likely to be women (P<0.001), to be younger (P<0.001 for both men and women), to be currently employed (P<0.001 for both men and women) and to be heavier (P<0.001) and to be former smokers (P<0.001 for both men and women) (see Table S4).

Compared to female dieters, male dieters tended to be older, more frequently former smokers, more frequently overweight or obese, and less likely to have followed more than one diet in the previous three years. (Table 1) Diet characteristics were also significantly different across genders: compared to female dieters, male dieters were less likely to select commercial diet plans (with or without coaching programs), and more likely to undergo self-imposed dietary restrictions (Table 2). Among the commercial diet plans, the Dukan diet was the most frequently cited in both men and women (Table S2). As to commercial diet coaching programs, Weight Watcher was the most represented (Table S2).

For all other analyses, results of cross-tabulations (comparison across diet types with Chi-square tests) are presented in Tables S3 and S4. Results of multivariate analyses are presented in Tables 3 and 4.

The prevalence of dieters in our sample is comparable to that reported in a representative sample of the French population.[30] However, compared to other international and particularly North American studies, the prevalence of weight-loss strategies in our population was relatively low.[9], [10]This can be related to the fact that dieting behaviors are closely related to BMI, and compared to the rates in the USA, France has a lower prevalence of overweight/obesity.[31], [32] Still, our interest was not characterization of dieters per se, or giving population-level estimates of dieting outcomes.

As hypothesized, circumstances and types of diets followed by men or women differed markedly. Gender differences in the prevalence of dieting have been consistently reported[9], [26], [27] and can be explained by double standards regarding the social pressure for thinness, driving body dissatisfaction.[33] Women start experiencing social (and even family) pressure for thinness and body dissatisfaction at a very early age,[34], [35] and therefore start dieting earlier and more repeatedly.

Consistent with our results, results from NHANES showed that strategies for losing weight differed according to gender: men were found to be more likely to exercise than were women and less likely to join a weight-loss program.[9], [27] Differing strategies for losing weight according to gender can be related to differing weight goals when dieting, with women tending to have higher weight loss goals than men.[27], [36] Our results extend these findings, showing that despite differences in the choices made by men and women in terms of diet strategies, their perceptions tend to be similar.

Diets prescribed by health professionals were associated with the most positive perceptions: they were perceived as being relatively easy to follow, as leading to reduced frustration, and more importantly, as being less likely to lead to weight regain or to dietary imbalance following cessation. Health professionals are likely to be aware of the importance of setting achievable goals for dieters[37], and of the health impact of even modest weight loss.[21] In fact, expert recommendations now tend to shift from low- and very-low-calorie diets to moderate restrictions[38], [39] concomitant with physical activity[40] in order to achieve progressive weight loss. Finally, health professionals personalize dietary advice to individual lifestyles and dietary preferences. They are often engaged in the individualized and active follow-up of their patients. All of these considerations could explain the positive perceptions that such diets generate.

On the other hand, commercial diet plans and self-imposed dietary restrictions appear to entail the least favorable perceptions. Popular commercial diets rely mostly on calorie restrictions regarding specific macronutrients and are often quite different from dietary recommendations.[41] The Dukan and Atkins diets, for example, are low-calorie diets with very low carbohydrate and very high protein intakes.[42] Thus, alterations in macronutrient supply can alter signals of hunger and satiety.[25], [43] Regardless of the macronutrient composition, the extent of calorie restriction has been negatively related to compliance with the diet.[44], [45] Such characteristics of commercial diet plans are likely to explain at least in part the negative outcomes we observed in terms of perceptions. Moreover, exercise concomitant with dietary restriction is also an important determinant of weight loss and weight-loss maintenance in the long term.[46] We observed that commercial diets were not likely to be followed in parallel with exercise. This result is consistent with those of a qualitative study in a sample of obese subjects indicating that whereas subjects engaged repeatedly in commercial diets, few engaged in physical activity.[47]

Following a generally balanced diet informed by official dietary recommendations appeared to be a well perceived strategy for losing weight, often equally favorably perceived as a diet prescribed by a health professional. In France, the Programme National Nutrition Santé is a national public health program aiming at improving through nutrition the health status of the general population.[29] Initially set in 2000 for a period of five years, it has regularly been renewed and is now in its third phase.[48] While public health objectives pertaining to the lowering of the prevalence of overweight and obesity are included in the program's framework, no specific dietary recommendations have been disseminated as to optimal weight.[29], [48] Here, we observed that these dietary recommendations have empowered subjects to balance their own diets in order to lose weight, leading to positive results. This could prompt authorities to enlarge current recommendations in order to encompass advice for weight maintenance and optimal weight. However, such dietary recommendations should be carefully developed in order not to increase the already substantial social pressure regarding thinness or the stigmatization of obese subjects.[49]

Among all dieting strategies, commercial coaching programs appeared to be midway between commercial diet plans and the adherence to recommendations as regards perceptions of the diet, feelings of hunger, frustration. Weight loss in commercial coaching programs is mostly related to retaining rate, with the most active subjects in the programs having the most beneficial results.[13], [50], [51] Participation in weight-loss programs is hindered by costs, as the most frequent motivation for dropping out of the program is its cost at the individual level.[52] This could explain in part our results, especially as regards subjects who were not able to complete the program for financial reasons even though they had perceived it positively.

In conclusion, our results show that beside diets prescribed by health professionals, which should be followed only in individually-determined clinical situations, counseling relying on dietary recommendations as they are disseminated in the general population could serve as a useful and well perceived strategy to achieve both dietary balance and weight control. Attention should be drawn to commercial diet plans, as they are both negatively perceived and give relatively poor results.