Energy expenditure at rest and during exercise in nonobese female cyclical dieters and in nondieting control subjects

The Physiological Effects of Weight-Cycling: A Review of Current Evidence

PURPOSE OF REVIEW

There is a common perception among the public that yo-yo dieting, defined as repeated cycles of weight loss followed by weight regain, results in accumulation of fat in the body and lower metabolic rate, thus hindering subsequent attempts to lose weight. We evaluated the effects of weight-cycling on body weight and body mass index (BMI), body composition including fat mass (FM) and lean body mass (LBM), and resting metabolic rate (RMR), by systematically reviewing existing scientific literature.

RECENT FINDINGS

Twenty-three cross-sectional and cohort studies (including subjects with a history of weight-cycling compared to those without such history) and interventional studies (evaluating physiological effects during one or more cycles of weight loss and regain) were identified, conducted in generally healthy adults across various age groups, races, and both genders, who had normal weight, overweight, or obesity. Eighteen studies investigated the association between weight-cycling and body weight or BMI, and thirteen of them found no significant association. Fifteen out of twenty studies also found no increase in FM, and none of eighteen studies found a decrease in LBM. Twelve out of fourteen studies reported no adverse changes in RMR either. The overwhelming majority of evidence suggests that weight-cycling (yo-yo effect) is not associated with any adverse effects in body weight, body composition, and metabolic rate. Accordingly, healthy individuals who struggle with overweight or obesity should not be discouraged from repeated attempts to lose the excess weight.

Adaptive Thermogenesis in Resistance to Obesity Therapies: Issues in Quantifying Thrifty Energy Expenditure Phenotypes in Humans

Dieting and exercise are likely to remain the core approaches in the management of obesity in the foreseeable future despite their well-documented failures for achieving long-term weight loss. Explanations for such poor prognosis are centered on patient's self-regulatory failure and lack of compliance to the prescribed diet or exercise regimen. While a role for physiological adaptations leading to diminished rates of heat production has also been advocated, there are considerable uncertainties about the quantitative importance of such regulated heat production (i.e., adaptive thermogenesis) to the less-than-expected weight loss and ease for weight regain. This paper first reviews the most compelling evidence of what is often considered as weight loss-induced adaptive thermogenesis in various compartments of daily energy expenditure. It then discusses the major limitations and issues in quantifying such thrifty energy expenditure phenotypes and underscores the plausibility of diminished core temperature as a thrifty metabolic trait in resistance to weight loss. Although an accurate quantification of adaptive thermogenesis will have to await the applications of deep body composition phenotyping and better discrimination of physical activity energy expenditures, the magnitude of diminished energy expenditure in response to weight loss in certain individuals is large enough to support the concept that adaptive thermogenesis contribute importantly to their resistance to obesity therapies.

Biological mechanisms that promote weight regain following weight loss in obese humans

Weight loss dieting remains the treatment of choice for the vast majority of obese individuals, despite the limited long-term success of behavioral weight loss interventions. The reasons for the near universal unsustainability of behavioral weight loss in [formerly] obese individuals have not been fully elucidated, relegating researchers to making educated guesses about how to improve obesity treatment, as opposed to developing interventions targeting the causes of weight regain. This article discusses research on several factors that may contribute to weight regain following weight loss achieved through behavioral interventions, including adipose cellularity, endocrine function, energy metabolism, neural responsivity, and addiction-like neural mechanisms. All of these mechanisms are engaged prior to weight loss, suggesting that these so called "anti-starvation" mechanisms are activated via reductions in energy intake, rather than depletion of energy stores. Evidence suggests that these mechanisms are not necessarily part of a homeostatic feedback system designed to regulate body weight, or even anti-starvation mechanisms per se. Although they may have evolved to prevent starvation, they appear to be more accurately described as anti-weight loss mechanisms, engaged with caloric restriction irrespective of the adequacy of energy stores. It is hypothesized that these factors may combine to create a biological disposition that fosters the maintenance of an elevated body weight and works to restore the highest sustained body weight, thus precluding the long-term success of behavioral weight loss. It may be necessary to develop interventions that attenuate these biological mechanisms in order to achieve long-term weight reduction in obese individuals.

Adaptive thermogenesis in human body weight regulation: more of a concept than a measurable entity?

According to Lavoisier, 'Life is combustion'. But to what extent humans adapt to changes in food intake through adaptive thermogenesis--by turning down the rate of heat production during energy deficit (so as to conserve energy) or turning it up during overnutrition (so as to dissipate excess calories)--has been one of the most controversial issues in nutritional sciences over the past 100 years. The debate nowadays is not whether adaptive thermogenesis exists or not, but rather about its quantitative importance in weight homoeostasis and its clinical relevance to the pathogenesis and management of obesity. Such uncertainties are likely to persist in the foreseeable future primarily because of limitations to unobtrusively measure changes in energy expenditure and body composition with high enough accuracy and precision, particularly when even small inter-individual variations in thermogenesis can, in dynamic systems and over the long term, be important in the determining weight maintenance in some and obesity and weight regain in others. This paper reviews the considerable body of evidence, albeit fragmentary, suggesting the existence of quantitatively important adaptive thermogenesis in several compartments of energy expenditure in response to altered food intake. It then discusses the various limitations that lead to over- or underestimations in its assessment, including definitional and semantics, technical and methodological, analytical and statistical. While the role of adaptive thermogenesis in human weight regulation is likely to remain more a concept than a strictly 'quantifiable' entity in the foreseeable future, the evolution of this concept continues to fuel exciting hypothesis-driven mechanistic research which contributes to advance knowledge in human metabolism and which is bound to result in improved strategies for the management of a healthy body weight.

Gestational weight gain as a predictor of longitudinal body mass index transitions among socioeconomically disadvantaged women

BACKGROUND

Socioeconomically disadvantaged women are at greater risk for gestational weight gain and postpartum weight retention compared to socioeconomically advantaged women. This study examines the effect of gestational weight gain on body mass index (BMI) transitions 5 years after pregnancy in socioeconomically disadvantaged women.

METHODS

Gestational weight gain was assessed in 2136 postpartum women participating in the Fragile Families and Child Well-being study who experienced full-term, singleton gestations. Longitudinal BMI transitions were defined as a change or stability in BMI category between two time points: BMI before the index pregnancy and BMI 5 years after the index pregnancy. Logistic regression models estimated the association between gestational weight gain and longitudinal BMI transitions, controlling for health before the index pregnancy, pregnancy history, and sociodemographic characteristics.

RESULTS

Excessive gestational weight gain was related to transitioning to a higher BMI category 5 years after the index pregnancy. Compared to white women, black and Hispanic women were more likely to transition or maintain a higher BMI category. Pregnancy history (i.e., parity at index pregnancy, interim pregnancy) and public assistance participation were associated with transitioning to a higher BMI category.

CONCLUSIONS

Among socioeconomically disadvantaged women, excessive gestational weight gain is related to transitioning to, but not maintaining, a higher weight category 5 years after the index pregnancy. Black and Hispanic women who are also socioeconomically disadvantaged and overweight or obese before conception may benefit from preconception or postpartum counseling about the long-term effect of gaining excessive weight during pregnancy and in the years immediately after childbirth.

Weight cycling during growth and beyond as a risk factor for later cardiovascular diseases: the 'repeated overshoot' theory

In people trying to lose weight, there are often repeated cycles of weight loss and regain. Weight cycling is, however, not limited to obese adults but affects people of normal weight, particularly young women, who are unhappy with their appearance. Furthermore, the onset of a pattern of weight cycling is shifting towards younger ages, owing to the increasing prevalence of overweight and obesity in children and adolescents, and the pressure from the media and society for a slim image even for normal weight children. Although there is still controversy whether weight cycling promotes body fat accumulation and obesity, there is mounting evidence from large population studies for increased cardiovascular risks in response to a behavior of weight cycling. Potential mechanisms by which weight cycling contributes to cardiovascular morbidity include hypertension, visceral fat accumulation, changes in adipose tissue fatty acid composition, insulin resistance and dyslipidemia. Moreover, fluctuations in blood pressure, heart rate, sympathetic activity, glomerular filtration rate, blood glucose and lipids that may occur during weight cycling--with overshoots above normal values during weight regain periods--put an additional load on the cardiovascular system, and may be easily overlooked if humans or animals are studied during a state of relatively stable weight. Overshoot of those risks factors, when repeated over time, will stress the cardiovascular system and probably contribute to the overall cardiovascular morbidity of weight cycling.

Mild calorie restriction induces fat accumulation in female C57BL/6J mice

This study investigated the effects of mild calorie restriction (CR) (5%) on body weight, body composition, energy expenditure, feeding behavior, and locomotor activity in female C57BL/6J mice. Mice were subjected to a 5% reduction of food intake relative to baseline intake of ad libitum (AL) mice for 3 or 4 weeks. In experiment 1, body weight was monitored weekly and body composition (fat and lean mass) was determined at weeks 0, 2, and 4 by dual energy X-ray absorptiometry. In experiment 2, body weight was measured every 3 days and body composition was determined by quantitative magnetic resonance weekly, and energy expenditure, feeding behavior, and locomotor activity were determined over 3 weeks in a metabolic chamber. At the end of both experiments, CR mice had greater fat mass (P < 0.01) and less lean mass (P < 0.01) compared with AL mice. Total energy expenditure (P < 0.05) and resting energy expenditure (P < 0.05) were significantly decreased in CR mice compared with AL mice over 3 weeks. CR mice ate significantly more food than AL mice immediately following daily food provisioning at 1600 hours (P < 0.01). These findings showed that mild CR caused increased fat mass, decreased lean mass and energy expenditure, and altered feeding behavior in female C57BL/6J mice. Locomotor activity or brown adipose tissue (BAT) thermogenic capacity did not appear to contribute to the decrease in energy expenditure. The increase in fat mass and decrease in lean mass may be a stress response to the uncertainty of food availability.

Methodological issues in weight cycling

Recent studies have suggested that weight changes may be related to disease risk independent of weight status. A critical step in testing this assertion is the measurement of weight change and so-called "weight cycling". However intuitive the concept of weight cycling may appear, research in this area is hampered by complex methodological issues. This article discusses various measures of nominal weight cycling, including the standard deviation, coefficient of variation, regression techniques, and cycles. A cycle is a sequence of a gain followed by a loss or vice versa. The various measures are compared in seven hypothetical cases created to illustrate their strengths and weaknesses. Superior performance of the cycles measure over the coefficient of variation, number of fluctuations, and simple regression methods is argued. The linkage of the cycles measure with the statistical theory of runs also provides a basis for testing the significance of weight fluctuations or other variables that may cycle, such as blood lipids, etc. The cycles measure and runs test provide a viable definition for identifying weight cycling and a tool for evaluating the critical amount of weight gained and/or lost in relationship to risk.

Validation of three predictive equations for basal metabolic rate in adults

Objective

To cross-validate three predictive set of equations for basal metabolic rate (BMR) developed by Schofield (Schofield database), Henry (Oxford database) and Cole (Oxford database) using mean values for age, weight, height and BMR of published studies.

Design

Literature review of studies published from 1985 to March 2002.

Setting

All studies selected used appropriate methods and followed conditions that met the criteria established for basal metabolism, were performed in healthy adults, and were not part of the Schofield or Oxford database.

Subjects

A total of 261 groups of men and women from 175 studies were selected and categorised in three age groups (18.5–29.9, 30.0–59.9, ≥60 years old) and three body mass index (BMI) groups (normal weight, overweight and obese).

Results

Linear regression and concordance correlation analysis showed that the three sets of equations had the same association and agreement with measured BMR, across gender, age, and BMI groups. The agreement of all equations was moderate for men and poor for women. The lowest mean squared prediction errors (MSPRs) were given by Henry equations in men and Cole equations in women. Henry and Cole equations gave lower values than Schofield equations, except for men over 60 years of age. Henry equations were the most accurate in men. None of the three equations performed consistently better in women.

Conclusion

These results support the use of Henry equations in men with a wide range of age and BMI. None of the proposed predictive equations seem to be appropriate to estimate BMR in women.

Reduced rate of fat oxidation: a metabolic pathway to obesity in the developing nations

The purpose of this article is to document the metabolic and environmental factors associated with the increased frequency of obesity in the developing nations. While the prevalence of obesity in the developed countries is caused by the increased consumption of calorie-dense foods, in the developing nations, because obesity coexists with undernutrition, additional factors are necessary to account for it. The evidence suggests that an important contributing factor for obesity in the developing nations is a reduced fat oxidation and increased metabolism of carbohydrate that has been brought about by the chronic undernutrition experienced during prenatal and postnatal growth. This shift toward a preferential metabolic use of carbohydrate rather than of fat results in an increased deposition of body fat. This tendency, along with the general decrease of energy expenditure in physical activity associated with urbanization, and the culturally mediated acceptance of fatness leads to obesity among populations from the developing nations. A joint effect of these factors is that in the developing nations obesity is associated with short stature resulting from developmental undernutrition, while in the developed countries obesity is associated with tall stature. It is hoped that future research will address the mechanisms whereby undernutrition increases the tendency toward obesity. Understanding how to modify fat oxidation could affect our ability to prevent weight gain among undernourished populations of the developing nations. Therefore, future research on the interaction of undernutrition and the development of obesity is of prime importance for anthropology concerned with the origins of human variability.

Metabolic assessment of female chronic dieters with either normal or low resting energy expenditures

BACKGROUND

Chronic dieting syndrome can have negative physiologic and psychological consequences. Metabolic differences between female chronic dieters with normal and with low resting energy expenditures (REEs) have not been fully examined.

OBJECTIVE

To determine whether differences existed between 2 groups (n = 15/group) of female chronic dieters aged 21-49 y with either normal (>/=100% of predicted) and with low (</=85% of predicted) REEs based on the equation of Mifflin et al.

DESIGN

The sample was a nonrandomized convenience sample and the 2 groups were compared in an observational study design. Body composition, aerobic fitness, physical activity, glucose and insulin responses, leptin and thyroid hormone status, dietary intake, and dietary restraint were measured.

RESULTS

Both groups were similar with respect to age, height, weight, and body mass index. The normal-REE group had a higher lean body mass and insulin response to a test meal, higher thyroxine and reverse triiodothyronine concentrations, and lower dietary restraint. Within both groups, leptin decreased significantly from baseline to 2 h after an oral-glucose-tolerance test. The groups did not differ significantly with respect to dietary intake, aerobic fitness, or physical activity.

CONCLUSIONS

Differences in insulin response were associated with higher ratios of abdominal to gluteal body fat in the normal-REE group. Leptin response appears to be due to normal diurnal variations in leptin production rather than a direct response to food consumption. It appears that a normal REE does not necessarily predict positive metabolic health among chronic dieters.

Chronic dieting in active women: what are the health consequences?

Evidence suggests that there is ever increasing pressure on American women to be thin. This pressure drives women to want to be thinner than what might be realistically achieved or required for good health. Our goal as nutrition and health professionals is to help women achieve and maintain a healthy body weight throughout the life-cycle. This includes helping young females accept their body size and shape as well and placing more emphasis on health and fitness than on weight in this population. This process begins with the identification of what constitutes a healthy body weight for a particular individual based on genetic, physiological, social, and psychological factors. In addition, it should be a weight that can be realistically maintained while keeping risk factors for chronic disease low. Table 1 outlines some strategies for helping individuals to identify and maintain a healthy body weight.

Weight Cycling: More Questions than Answers

Most men and women who attempt to lose weight will regain any weight that is lost. This cycle of weight loss and regain - referred to as weight cycling is a recurrent phenomenon for many patients. With the increased frequency of obesity and the increased prescriptions for weight-loss practices without an associated increase in the success of weight-loss maintenance, the concerns about weight cycling have grown. Recent literature has focused on the possible physiologic and psychologic hazards of weight cycling. Review of both human and animal studies indicates no conclusive evidence about harmful effects of weight cycling. Most studies show no adverse effects on metabolism. Some observational studies indicate an association between variations in body weight and increased morbidity and mortality but do not distinguish between voluntary and involuntary weight-loss events. The studies of psychologic hazards have been limited, and little convincing information is available. Without more compelling evidence of the risks of weight cycling, warnings overriding safe, effective weight-loss treatments for the obese are unwarranted. Appropriately designed studies are urgently needed to assess the long-term efficacy of procedures and treatments that promote weight-loss maintenance and to provide further analyses of the effects of weight cycling.

Metabolic and anthropometric changes in female weight cyclers and controls over a 1-year period

OBJECTIVE

Women who diet to lose weight often regain the weight over time, and the cycle repeats itself. The objective of this study was to identify a group of female weight cyclers and to match them with a control group who had never consciously tried to lose weight. For 1 year, weight patterns, eating habits, metabolic parameters, and body composition were assessed to determine whether there was a relationship between weight cycling and these variables.

DESIGN

Measurements were done at baseline and at 6 and 12 months. Changes in weight, diet, and exercise were monitored throughout the year.

SETTING

All testing was done at a university physiology laboratory.

SUBJECTS/SAMPLES

Nine weight cyclers with a notable history of dieting and food restriction were recruited. Subsequently, nine control subjects were selected and matched for age, height, weight, lean body mass, and exercise habits.

MAIN OUTCOME MEASURE

The observational study included measures of 3-day diet records, skinfold and girth, serum glucose, insulin and triiodothyronine, and resting energy expenditure.

STATISTICAL ANALYSES PERFORMED

The main variables were analyzed using a 2 x 3 (diet group x time) analysis of variance with repeated measures on the time factor. Comparison of the means was done by Tukey post hoc test.

RESULTS

A 7-point satisfaction scale indicated that the weight cyclers were dissatisfied with their weight compared with the noncyclers (P = .03). Otherwise, there were no differences between groups in dietary intakes or the physiologic variables.

APPLICATIONS/CONCLUSIONS

In the parameters measured, a history of weight cycling did not affect the metabolic profiles of the weight cyclers compared with the noncyclers.