yo-yo-diet
yo-yo-diet

What is a yo yo diet

A Yo-yo diet is often called weight cycling, which is the repeated weight loss and regain of body weight on some particular diet. Repeated bouts of weight loss followed by regain forms a pattern known as weight cycling. Weight cycling or ‘yo-yo’ dieting is an inevitable process in human, because of subsequent weight loss and regain of body weight due to poor diet and irregular dieting. Human weight cycle (yo-yo dieting) is the major factor for causing global epidemic diseases in human beings 1). Research indicates that weight cycling, or “yo-yo dieting” is a common occurrence in overweight and obese populations. The long term negative health consequences of weight cycling are debated and it is unclear whether or not this weight change pattern poses a greater disease risk compared to obesity maintenance 2).

Every year, scores of millions of people – as diverse as obese and lean, teenagers and older adults, sedentary and elite athletes, commoners and celebrities – attempt to lose weight on some form of diet. People on the yo-yo diet or weight cycling can usually change their body weight from small weight loss and to small weight regains of 5-10 lbs per cycle, to large body weight changes in weight of 50 lbs. or more per cycle. The National Institutes of Health suggest that small weight cycles range from loss and regain of 2.3–4.5 kg, whereas a large cycle may be characterized by 23 kg or more 3). Weight regain is generally the rule, with one-third to two-thirds of the weight lost being regained within 1 year and almost all is regained within 5 years 4). With studies of the long-term outcomes showing that at least one-third of dieters regain more weight than they lost, together with prospective studies indicating that dieting during childhood and adolescence predicts future weight gain and obesity, there is concern as to whether dieting may paradoxically be promoting exactly the opposite of what it is intended to achieve.

It has been estimated 24% of American men and 38% of women are currently attempting to lose weight 5), 6), 7). When individuals with an obese body mass index (BMI) are considered, 65% of men and 68% of women are trying to lose weight, which is a fivefold increase compared to those within the normal BMI (18–24.9 kg/m2) range that are trying to lose weight 8). While successful weight loss is achieved, researchers have indicated that long-term maintenance of a reduced weight appears to be rare.

The probability of weight regain increases in the time following initial weight loss 9). Researchers believe this is due to the energy gap created during caloric restriction where decreased energy expenditure is paired with an increased drive to eat 10). Rodent studies have demonstrated that this gap persists regardless of the duration of weight reduction, which increases the probability of weight regain 11). This drive to eat causes a hyperphagic response when free access to food is allowed and when paired with suppressed lipid utilization, weight regain is often rapid and efficient 12), 13). While this finding was elucidated through use of a rodent model, human weight regain data supports this concept. One year after a modest weight loss (14.5% of body weight), Votruba et al. 14) reported that within a year of weight loss, 16 out of 28 women regained weight and had a 19% increase in body weight and a 26% increase in percent fat mass. Weiss 15) reported that by one year after a modest weight loss (10% of body weight), 33% of adult subjects regained all lost weight. Furthermore, they concluded that the odds of regaining were positively associated with the percentage of initial weight lost 16). Field et al. reported that approximately 55% of overweight and obese women who lost 10% of their body weight regained all lost weight within 4 years 17). In support of this finding, within 9 years of the initial weight loss (5% of body weight), 95% of women and 93% of men were unable to maintain the reduced body weight 18). Collectively, these studies suggest that while initial weight loss is possible, long-term maintenance is problematic, especially when large amounts of weight are lost or an individual is overweight or obese.

Some research links weight cycling or yo-yo dieting with certain health risks. To avoid potential risks, most experts recommend that obese adults adopt healthy eating and regular physical activity habits to achieve and maintain a healthier weight for life. Non-obese adults should try to maintain their weight through healthy eating and regular physical activity.

Links between yo-yo diet and increased body weight, hypertension and eating-disordered cognitions have been proposed, however, studies on the physical and/or psychological health risks associated with yo-yo diet have produced mixed results. Some studies report no relation between yo-yo diet and physical health 19), while others suggest that cycling increases health risks. Specifically, yo-yo diet has been associated with increased weight and central adiposity 20), 21), hypertension (high blood pressure) 22), 23) and type 2 diabetes 24).

Who are the demographic of yo-yo dieters

According to research yo-yo dieters and non-yo-yo dieters did not differ on demographic information including age, education, employment status, income, marriage, or medication use 25). See Table 1 for a list of all demographic information.

Survey data collected by Williamson and colleagues 26) indicated that 25% of men and 27% of women trying to lose weight have made long-term attempts (classified as trying for over 1 year or “always trying to lose weight”). It has also been shown that 7% of men and 10% of women can be classified as severe weight cyclers (intentionally lost at least 5 kg and regained at least three different times), while 11% of men and 19% of women are mild weight cyclers (lost and regained at least 5 kg on one or two occasions) 27). While these results were generated from a group of adults in Finland, the conclusion that 18% of men and 27% of women weight cycle is comparable to the prevalence described by Williamson et al. 28). These numbers are likely a conservative estimate of the prevalence of weight cycling, which may be even greater in the United States.

Table 1. Demographic information of Yo-yo dieters and Non-yo-yo dieters

      Yo-yo dieters     Non-yo-yo dieters
Age41.5741
Education, ≥16 years52%50%
Full-time employment90%95%
Individual income, >$40,00067%65%
Married47%60%
Hypertension classification, mm Hg
 Normal, <120/<8028%32%
 Pre-HTN, 120–139/80–8944%46%
 Stage 1 HTN, 140–159/90–9921%19%
 Stage 2 HTN, >160/>1006%4%
[Source 29)]

Note: HTN = hypertension (high blood pressure)

Interestingly, more than half of yo-yo dieters had tried yo-yo diet more than three times. Yo-yo dieters weighed more, had a higher body mass index (BMI) and reported a higher peak weight compared to non-yo-yo dieters, despite reporting no differences in ideal weight.

Yo-yo dieters were more likely to binge eat and reported greater body image disturbance.

Yo-yo dieters reported significantly lower self-esteem for their appearance and greater body dissatisfaction and drive for thinness compared to non-yo-yo dieters, however, all self-esteem scores were within clinically normal limits 30). Average total self-esteem scores, symptoms of anxiety, and symptoms of depression were all clinically non-significant and did not differ between yo-yo dieters and non-yo-yo dieters, suggesting that the relationship between psychological health and yo-yo dieters may be limited to the domain of body image and eating 31), 32).

Does Weight Regain in Yo-yo Diet Disrupts Normal Physiology ?

The physiological changes associated with weight cycling, such as energy expenditure, metabolism and fuel utilization, have been documented using a rat model. MacLean and colleagues 33) have documented the physiological alterations occurring in obesity-prone rats that contribute to the rapid, efficient regain during relapse following weight loss and maintenance. Their focus has been on the energy gap created during a period of caloric restriction that is characterized by decreased energy expenditure and an increased drive to eat 34). They found that in addition to changes in energy intake, alterations in metabolic efficiency and fuel utilization (favoring carbohydrate oxidation) may significantly affect the propensity to regain weight 35). For instance, in the 16 weeks following moderate weight loss (14%), food efficiency was increased 10-fold upon the first day of a 56-day re-feeding in weight cycle rats compared to rats with established obesity. While this dramatic rise was reduced within several days, food efficiency remained elevated above levels in obese mice for the first 4 weeks of relapse 36). The most dramatic changes occurred during the first week of relapse, a time when nearly 40% of lost weight, which was primarily fat mass, was regained 37), 38). Researchers also noted that as the length of maintenance increased, the amount of weight regained upon relapse also increased. Furthermore, regain was accompanied by a 30% increase in adipocyte concentration per fat pad.

Based on the above literature, it is clear that weight gain during relapse appears to induce more rapid adipose tissue growth and hyperplasia due to metabolic shifts favoring lipid storage. Because adipose tissue is a metabolically active tissue, responsible for production of leptin, cytokines and adiponectin as well as responding to traditional hormone systems 39), it is possible that the consequences of weight gain during relapse may also differ from that of initial weight gain. In recent years, lay literature has asserted that weight cycling may be more detrimental to health than simply remaining overweight or obese 40), 41). Researchers have found associations between weight cycling and an overshoot of lipogenic enzyme, triglyceride and cholesterol levels in animals and increased risk of heart attack and stroke in humans 42), 43), 44), 45). However, other researchers noted no long term adverse effects on body composition, blood pressure, lipid profile or risk of developing type II diabetes 46), 47), 48), 49), 50) (13, 22, 37, 49, 56). Due to limited research in the area of weight cycling all of the negative consequences may not be known. Existing studies differ considerably in their research design, subject population used, duration of treatment, incorporation of exercise, magnitude and frequency of weight cycles. The lack of a universal definition of weight cycling is perhaps a great contributor to the variability within experimental design. This variability is discussed in greater detail in the following sections.

Evaluation of Weight Cycling: Human Models

Some existing scientific literature supports the theory that weight cycling increases disease risk (directly or indirectly) in humans. Wallner and colleagues 51) found that a history of weight cycling was associated with a more pronounced android fat distribution in women compared to those who were normal-weight or overweight without a history of weight cycling 52). It is possible that women who are prone to the accumulation of abdominal adiposity may be more likely to weight cycle for a more aesthetically desirable figure 53). Regardless of whether weight cycling causes the accumulation of android adiposity or vice versa, other researchers have found that a history of weight cycling was independently associated with an increased risk of developing hypertension 54) and clinically significant decreases in HDL-cholesterol in women 55). French et al. 56) and Vergnaud et al. 57) demonstrated associations between weight cycling and risk for heart attack and stroke, as well as the development of metabolic syndrome 58), 59). Blair et al. 60) studied men enrolled in the Multiple Risk Factor Intervention Trial who were at elevated risk for coronary heart disease due to smoking, hypertension and hypercholesterolemia, finding that greater weight variability over 4 years of follow up was associated to increase all-cause mortality.

In contrast to the preceding reports, several other researchers reported that weight cycling has no independent impact on health status. Prentice et al. found that weight cycling did not significantly alter body composition 61). However, unlike Wallner et al. 62), who asked for 4 years worth of weight history, this study was completed in only 18 weeks. It may be possible that any deleterious effects of weight cycling do not manifest immediately or that the magnitude of the weight loss was not sufficient to induce long-term change. Li et al. 63) studied obese patients, in a multi-disciplinary weight loss program, who had relapsed and re-entered. Multiple attempts at weight loss over 12 years showed no effect on the rate at which weight could be lost each time or on blood pressure or lipid profile; in fact, these measurements at baseline were significantly lower at the time of re-entry compared to the initial start for men and women. Initial blood pressure in men (134/88 mmHg) and women (126/82 mmHg) was recorded at the restart baseline at 129/85 mmHg and 121/78 mmHg, respectively. While no subjects were hypertensive, all values remained within the pre-hypertensive range. Furthermore, BP has been documented to fluctuate throughout the day 64). Triglyceride levels in men and women were reduced by 0.1 and 0.2 mmol/L between initial and restart baselines and cholesterol was reduced by 0.1 and 0.5 mmol/L, respectively. Women’s values were all within the normal/low risk range and men’s values remained in the borderline high range. Cholesterol values for both genders were all in the borderline high risk range. While deemed statistically significant, the differences between baselines may not be physiologically relevant as disease risk did not appear to change. Even though this study was longitudinal in nature, perhaps the use of regular exercise as part of the program acted as a confounding factor, as aerobic exercise is independently and positively correlated with decreases in blood pressure and cholesterol 65), 66).

A similar exercise effect was reported by Field et al. 67) where mild and severe weight cycling was strongly associated with weight gain and hypertension, controlling the statistical analysis for weight and weight gain greatly attenuated this correlation; however, the questionnaire data also revealed that severe weight cyclers exercised significantly more that non weight cyclers. Graci et al. 68) noted that weight cycling had no effect on cardiovascular disease risk factors; weight cycling throughout adulthood was not associated with changes in body composition, fat distribution blood pressure or insulin levels. One major difference in this study, compared to those with competing findings, was that Graci et al. 69) used morbidly obese subjects (BMI up to 69 kg/m2) and perhaps there is a less-pronounced response to weight cycling in this population because the subjects already have an elevated disease risk. Similar results by Wing et al. 70) and Jeffery et al. 71) may have been effected by the short duration of measurement period (2.5 years) or the failure to use appropriate blood pressure cuffs for obese patients 72). Field et al. 73) concluded that 4 years of weight cycling, prior to diagnosis of type 2 diabetes, was not predictive of disease development while Wannamethee et al. 74) and Mehta et al. 75) found that weight fluctuation does not directly increase risk of death.

There is only one published study that examined the effect weight variability has on pro-inflammatory or related factors. Yatsuya et al. 76) reported that Japanese men with a history of weight variability had an independently increased odds ratio of elevated C-Reactive Protein (CRP). One limitation of this study was that it was a cross-sectional design thus it was not possible to evaluate cause and effect, no information on intentionality of weight change and the cross-sectional design with a majority of subjects having final BMIs less than 25 kg/m2. This lack of literature suggests that in order to fully understand the possible effects of weight cycling, we must include examination of pro-inflammatory responses to this pattern.

Yo yo diet consequences on health

As obesity is becoming increasingly more prevalent in the United States, weight loss to reduce adipose tissue mass is strongly promoted as a means to decrease the disease risk associated with excess adiposity 77), 78). Unfortunately, the majority of individuals who lose weight are unlikely to maintain the reduced weight for an extended period of time 79), 80). Repeated periods of weight loss and regain form a pattern known as weight cycling or yo-yo dieting. Hill 81) indicates that popular and lay literature have asserted that weight cycling (i.e. “yo-yo dieting”) may increase the risk of developing cardiovascular disease or type II diabetes to a greater extent than remaining weight stable at an obese Body Mass Index (BMI; ≥30 kg/m2). The scientific literature is inconsistent regarding the long-term consequences of weight cycling. Because there is no universally-accepted definition of yo-yo dieting, differences in experimental design may have contributed to discrepancies in scientific outcomes.

Weight gain and obesity have significant implications concerning disease risk, which is believed to be mediated by an elevated level of systemic inflammation. Low-grade systemic inflammation is associated with obesity and it may serve as a link between adiposity and the development of cardiovascular disease and type 2 diabetes 82). The pro-inflammatory effects of yo-yo dieting have not been examined. Discerning a difference in disease risk between maintenance of obesity and yo-yo dieting is important and may provide insight concerning individual differences in disease progression. If yo-yo dieting is associated with an increased disease risk, continually recommending weight loss to those unable to maintain reduced weights may be a major public health issue.

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