Obesity is now recognized as a serious chronic disease; in my post titled Is obesity a disease or a risk factor for other conditions? I had discussed the magnitude of obesity and why obesity is associated with so much ill-health. However, there are no easy solutions to obesity and managing your body weight is challenging at the best of times. In my post titled Weight Loss Maintenance After Weight Loss, I had discussed how over the long term, the vast majority of individuals regain the weight they have lost and that this relapse has a strong physiological basis and is not simply the result of the voluntary resumption of old habits. Some evidence suggests, however, that a high cardiorespiratory fitness (CRF) might mitigate the detrimental effects of excess body weight on cardiometabolic health, termed the ‘fat but fit’ paradox.
Recognition of the ‘fat but fit’ paradox
In my post, Complications of obesity: the mother of all diseases, I had discussed the various health complications associated with obesity. However, accumulating evidence over the years suggests that being physically fit might attenuate some of the deleterious health consequences of obesity independently of some key potential confounders. About 3 decades ago, a study titled ‘Physical Fitness and All-Cause Mortality: A Prospective Study of Healthy Men and Women’ published in the Journal of the American Medical Association in Nov 1989, brought into focus the detrimental role of fitness (cardiorespiratory fitness [CRF]) vis-à-vis fatness on health, specifically all-cause mortality and CVD-related mortality. This longitudinal study followed up 10,224 men and 3120 women for slightly more than 8 years. The study found that better CRF, as measured by a maximal exercise test, was associated with decreased all-cause mortality in both sexes. Based on the maximal treadmill test, participants were stratified into quintiles of fitness categories. Age-adjusted all-cause mortality rates declined across physical fitness quintiles from 64.0 per 10,000 person-years in the least-fit men to 18.6 per 10,000 person-years in the most-fit men (fat but fit). Corresponding values for women were 39.5 per 10,000 person-years to 8.5 per 10,000 person-years. Lower mortality rates in higher fitness categories also were seen for cardiovascular disease and cancer of combined sites. Higher levels of physical fitness appear to delay all-cause mortality primarily due to lowered rates of cardiovascular disease and cancer.
Even though the term ‘fat-but-fit’ was coined, later on, two key studies supporting this concept were published in 1999. The first study titled ‘Relationship between low cardiorespiratory fitness and mortality in normal-weight, overweight, and obese men’ published in Journal of the American Medical Association in Oct 1999, followed up 25714 men (average age, 43.8 years [SD + 10.1 years]). The study is based on data from the Aerobics Center Longitudinal Study (ACLS), an observational study of patients examined at a preventive medicine clinic in Dallas, Tex, from 1970 to 1993. Men were stratified into BMI groups using the internationally accepted cut points and were categorised into two cardiorespiratory fitness groups – unfit (belonging to the first age-specific quintile) and relatively fit (when belonging to the second to fifth age-specific quintiles). The study found that men who were fat but fit had a marginally higher risk of CVD mortality than normal-weight and fit men. On the contrary, this risk was 50% lower than that observed in normal-weight but unfit men and was also dramatically lower than the risk observed in obese and unfit men. The study concluded that low cardiorespiratory fitness was a strong and independent predictor of CVD and all-cause mortality and of comparable importance with that of diabetes mellitus and other CVD risk factors. The authors went on to suggest that clinicians should evaluate fitness in their patients just as they now obtain a medical history and measure blood cholesterol and plasma glucose levels. Evaluating fitness, or at least physical activity allows for more complete risk stratification in overweight and obese patients and can enhance clinical decision making. These findings support two relevant public health messages:
- In obese persons, even being relatively fit (i.e. not falling in the bottom quintile of age-adjusted cardiorespiratory fitness level) significantly reduces the risk of CVD mortality, thereby suggesting that regularly engaging in aerobic exercises to improve cardiorespiratory fitness might have important long-term health benefits, even if it does not result in any weight loss (i.e. fat but fit).
- Obese people who are physically fit might have a lower risk of CVD mortality compared to normal weight but physically unfit persons, suggesting that being normal-weight might not be enough to ensure optimal CV health; instead being physically fit plays a major role in health. This busts the myth that being normal weight is synonymous with being healthy. Improving cardiorespiratory fitness through PA and physical exercise should therefore be a public health recommendation in any case.
Another study titled ‘Cardiorespiratory fitness, body composition and all-cause and cardiovascular disease mortality in men’ published in The American Journal of Clinical Nutrition in March 1999, examined the health benefits of leanness and the hazards of obesity while simultaneously considering cardiorespiratory fitness. The study followed 21925 men, aged 30 – 83 years, who had a body composition assessment (the study used skinfold thickness or hydrostatic weighing for assessing body composition, instead of BMI) and a maximal treadmill exercise test, for an average of 8 years; participants were divided into 3 groups according to their body fat percentage. Besides, the study aimed to test the impact of abdominal obesity instead of overall adiposity or body weight, on the fat-but-fit concept. For this purpose participants were categorised into 3 groups according to their waist circumference (WC). Finally, cardiorespiratory fitness groups were defined using the categorization method described above. Results based on the body fat percentage groupings were similar to the study using BMI groups, discussed above. Obese men who were fit (fat but fit) had a markedly lower risk of CVD mortality than those who were obese and unfit and even lower than those who were normal-weight and unfit. Similarly, men with high WC but fit had a markedly lower risk of mortality than those with high WC and unfit and also than those with a low WC but unfit. Thus, the study strongly supports the hypothesis that cardiorespiratory fitness might counteract the adverse effects of an excess of total and abdominal adiposity on the cardiovascular system in men. The study concluded that the health benefits of leanness are limited to fit men, and being fit may reduce the hazards of obesity.
The authors went on to suggest that for long-term health benefits we should focus on improving fitness by increasing physical activity rather than relying only on diet for weight control. Aerobic exercise improves IHD risk factors, and increases in physical activity or fitness extend longevity. People with obesity should be encouraged to increase their cardiorespiratory fitness by engaging in regular, moderate-intensity physical activity; this should benefit them even if they remain overweight (i.e. fat but fit).
‘Fat but fit’ paradox in women
A decade later, the above hypothesis was tested in women too. A study titled ‘The Association Between Cardiorespiratory Fitness and Risk of All-Cause Mortality Among Women With Impaired Fasting Glucose or Undiagnosed Diabetes Mellitus’ published in the journal Mayo Clinic Proceedings in Sep 2009, evaluated the independent and joint associations among cardiorespiratory fitness, body mass index, and risk of mortality from any cause among 3044 women with impaired fasting glucose (IFG) or undiagnosed diabetes mellitus (DM). The study concluded that cardiorespiratory fitness, not body mass index, is a significant predictor of all-cause mortality among women with IFG or undiagnosed DM, independently of traditional risk factors. It went on to add that assessing CRF levels provides important prognostic information independent of traditional risk factors. More importantly, the study demonstrated the applicability of the fat-but-fit concept in women with impaired fasting insulin or diagnosed type 2 diabetes mellitus.
Another study titled ‘Cardiorespiratory Fitness, Adiposity and All-Cause Mortality in Women’ published in the journal Medicine and Science in Sports and Exercise in Nov 2010, examined the prospective associations among cardiorespiratory fitness (CRF), different measures of adiposity, and all-cause mortality in 11,335 apparently healthy women. Besides BMI, the study additionally focused on other measures of adiposity such as body fat %, waist circumference and waist-to-hip ratio. The study concluded that low CRF in women was a significant independent predictor of all-cause mortality. Higher CRF was associated with lower mortality within each category of adiposity exposure. Using adiposity measures as predictors of all-cause mortality in women may be misleading unless CRF is also considered. Therefore, physicians and other healthcare professionals should make a concerted effort to estimate or measure CRF levels before categorising patients into risk strata based on adiposity exposures only.
Furthermore, the authors found that only a relatively modest level of CRF is necessary to obtain significant protection. In the present study, a much greater incremental reduction in mortality risk was achieved comparing low to moderate CRF (~40% reduction) than from comparing moderate to high CRF (~10% reduction), supporting the premise that it may be possible to achieve a sizable reduction in all-cause mortality simply by encouraging women of low CRF levels, including those who are obese, to achieve moderates CRF levels. The authors opined that it is very likely that if women follow current public health guidelines for physical activity, i.e. 150 min/week of moderate-intensity aerobic exercise, then these modest moderate levels of CRF can be achieved by a substantial proportion of adult women.
In sum, the main findings of these two studies in women are in consonance with the findings in men. Fat-but-fit women had a markedly lower risk of mortality than fat and unfit women and also lower mortality than normal-fat but unfit women, independently of the adiposity markers used i.e. BMI, BF% or WC.
Recent data on ‘fat but fit’ paradox
Some more recent studies have also supported the fat-but-fit paradigm. A meta-analysis titled ‘Fitness vs. Fatness on All-Cause Mortality: A Meta-Analysis’ was published in the journal Progress in Cardiovascular Diseases, Jan-Feb 2014 issue, assessed the relative influence of BMI and CRF on all-cause mortality. The meta-analysis included 10 studies with 92,986 participants. The study found that compared to normal weight-fit (fit defined as being above the bottom quintile or tertile of age- and sex-related CRF) individuals, unfit individuals had twice the risk of mortality regardless of BMI. However, compared with normal weight-fit individuals, there was no significant increase in mortality risk among overweight and obese-fit individuals. These findings have important public health implications. The study suggested that researchers, clinicians and public health officials should focus on PA-based interventions rather than weight loss driven approaches to reduce mortality risk. Much more attention should be given to promoting PA and CRF as a means to reduce the risk of disease and death.
Another study titled ‘Fitness, Fatness, and Mortality: The FIT (Henry Ford Exercise Testing) project published in The American Journal of Medicine in Sep 2016, examined the relative impact of exercise capacity and body mass index (BMI) on all-cause mortality. The study followed a racially and ethnically diverse population of 29,257 for a mean of 10.8 years. The study concluded that reduced exercise capacity was a strong independent risk factor for all-cause mortality in this racially diverse population. In contrast, the impact of BMI was comparatively limited, thereby suggesting that more emphasis should be placed on measuring exercise capacity and developing strategies for its improvement in cardiovascular disease prevention programs.
Fat but fit paradox in patients with co-morbidities
Besides the study discussed above, some other studies have also tested the fat-but-fit paradigm in individuals with pathological conditions related to CVD, such as type 2 diabetes mellitus and hypertension. A study titled ‘Cardiorespiratory fitness and body mass index as predictors of cardiovascular disease mortality among men with diabetes published in the journal Archives of Internal Medicine in October 2005, examined the independent and joint relations of cardiorespiratory fitness and body mass index with CVD mortality in men with diabetes. In this cohort of men with diabetes, the study found that low fitness level was associated with increased risk of CVD mortality within normal weight, overweight, and class I obese weight categories. In line with the recommendations of the studies discussed above, the author suggested that medical care providers should give increased attention to counselling for increasing activity and improving fitness in their patients with diabetes, both for the intrinsic benefits associated with increased fitness and for the critical role regular physical activity plays in the long-term weight loss maintenance.
Another study titled ‘The joint effects of cardiorespiratory fitness and adiposity on mortality risk in men with hypertension published in the American Journal of Hypertension in Oct 2009 examined whether higher cardiorespiratory fitness (CRF) attenuates the mortality risk associated with higher adiposity in adults with hypertension (HTN). The study followed 13,155 men, all of whom had HTN at baseline for a mean period of 12 years. The study found that higher levels of CRF were associated with lower all-cause and CVD mortality risk regardless of obesity status defined by BMI, WC, or BF%. Hypertensive men of normal weight survived better only if there registered high fitness (i.e. lean but fit).
Importantly, in line with the findings of a study discussed above, the incremental reduction in CVD mortality risk was greater from low to moderate (~50%), than moderate to high fitness (~20%) supporting the premise that it may be possible to achieve a sizable reduction in CVD mortality simply by encouraging hypertensive individuals of low fitness, including those who are obese, to achieve moderate fitness. Also, the favourable effects of regular exercise on blood pressure and improved fitness in patients with HTN may, in turn, reduce hypertensive medication use along with associated healthcare costs.
Visceral adiposity and ‘fat but fit’ paradox
In my post Waist Size: Measure your waist, measure your risk, I had highlighted that not all fat is the same; it is the intra-abdominal fat that is responsible for the various metabolic abnormalities and increased risk of type 2 diabetes and cardiovascular diseases. Various studies have examined the role of CRF in attenuating the risk associated with visceral adiposity. A study titled ‘Combined Impact of Cardiorespiratory Fitness and Visceral Adiposity on Metabolic Syndrome in Overweight and Obese Adults in Korea’ was published in the journal PLoS One in Jan 2014. The study determined the combined impact of cardiorespiratory fitness and visceral adiposity, otherwise known as fitness and fatness, on metabolic syndrome in overweight and obese adults. Visceral adipose tissue was measured using CT scan, a gold standard measure of visceral adiposity. The study concluded that more viscerally obese but fit (fat but fit) subjects had a lower risk of having metabolic syndrome than viscerally lean but unfit subjects. This suggests that cardiorespiratory fitness is a significant modifier in the relation of visceral adiposity to adverse metabolic outcomes in overweight and obese individuals. Therefore, improvement in fitness can be an important target for the maintenance of the overall healthy metabolic characteristics in overweight and obese individuals.
With ageing, most people gain weight and become less fit. A study titled ‘Long-Term Effects of Changes in Cardiorespiratory Fitness and Body Mass Index on All-Cause and Cardiovascular Disease Mortality in Men: The Aerobics Centre Longitudinal Study’ published in the journal Circulation in Dec 2011 examined 14,345 men (mean age 44 years) to determine whether age-related increases in BMI and reductions in CRF were associated with increased all-cause and CVD mortality. After adjusting for potential confounders, including BMI, every 1-MET equivalent increase in CRF was associated with 15% and 19% lower risk of all-cause and CVD mortality, respectively. In contrast, BMI change was not associated with all-cause or CVD mortality after adjusting for possible confounders and fitness change. In the combined analysis, men who lost fitness had higher all-cause and CVD mortality risks regardless of BMI change. The study concluded that maintaining or improving fitness is associated with a lower risk of premature deaths from all causes and CVD in men. Preventing fitness loss with age, regardless of whether BMI changes, is important for mortality risk reduction. Maintaining or improving fitness may also attenuate some potentially negative effects of weight gain on mortality. To date, extensive attention has been given to weight loss. However, the long-term effect of fitness change, primarily resulting from increasing physical activity, is likely to be at least as important as weight loss for reducing premature mortality. Therefore increase attention needs to be placed on strategies to maintain or improve fitness.
Prevalence of Fat-but-Fit
A study titled ‘The “fit but fat” concept revisited: population-based estimates using NHANES’, published in The International Journal of Behavioural Nutrition and Physical Activity in May 2010, estimated the proportion of US adults who are obese yet have a high cardiovascular fitness level, using the US nationally representative sample of 4675 adults aged 22 to 49 years from the National Health and Nutrition Examination Survey (NHANES). Considering the sampling and weighing methods used in NHANES, this analytic sample size was equivalent to a population-based sample size of 143,225,503 subjects. Based on cardiorespiratory fitness, individuals were categorised into low, moderate, and high cardiovascular fitness levels, and based on body weight they were categorised into normal weight, overweight and obese. The prevalence of fat but fit among US adults was 8.9%, whereas 17.4% were overweight and high fit, 30% were normal weight and high fit. However, the study defined fit as having a high cardiorespiratory fitness level (top 40%); this is different from the definition used in all the studies discussed above, in which unfit was considered when having a low cardiorespiratory fitness level (20% least fit or bottom quintile in age- and sex-based cardiorespiratory fitness) and fit when having a medium or high cardiorespiratory fitness level (80% most fit).
The review article ‘Obesity and Cardiovascular Disease referred to above, calculated the prevalence of fat-but-fit from the above data using the definition of fat-but-fit used in the literature. Based on the standard definition the authors estimated that the prevalence of fat-but-fit in the United States would be ~17%.
Physiological mechanisms underlying the beneficial role of exercise in the ‘fat but fit’
The physiological explanation for the fat-but-fit paradigm is that regular exercise has a favourable effect on many of the established risk factors for cardiovascular disease, and this remains true within individuals with obesity; as a result, fitness is able to counteract the adverse effects of obesity on CVD risk factors reducing, therefore, the risk of CVD mortality. In this context, a review article titled ‘Obesity and Cardiovascular Disease’, published in the journal Circulation Research in May 2016, analyzed the obese samples of the Aerobics Center Longitudinal Study (ACLS; A major contributor to consistently demonstrate the power of cardiorespiratory fitness as a predictor of CVD morbidity and mortality) and tested whether the risk of having CVD risk factors according to the metabolic syndrome definition was reduced in fit individuals. The results support that fat but fit individuals have a markedly reduced risk (ranging between 25% and 46% lower) of having CVD risk factors and a reduced risk of having metabolic syndrome compared with obese unfit individuals, contributing to explain the fat-but-fit paradigm relation with CVD mortality.
The various health benefits of exercise have been discussed in detail in my post titled Health Benefits of Exercise: a grossly underutilised therapy. Besides, in my post Metabolically Healthy Obesity – A Myth or a Reality, the role of greater cardiorespiratory exercise and physical activity in obese but metabolically healthy phenotype has been discussed in detail. However, in brief, exercise can reduce “bad” cholesterol levels in the blood (the low-density lipoprotein [LDL] level), as well as total cholesterol, and can raise the “good” cholesterol (the high-density lipoprotein level [HDL]). In diabetic patients, regular activity favourably affects the body’s ability to use insulin to control glucose levels in the blood. Besides, exercise promotes weight reduction and can help reduce blood pressure. Although the effect of an exercise program on any single risk factor may generally be small, the effect of continued, moderate exercise on overall cardiovascular risk, when combined with other lifestyle modifications (such as proper nutrition, smoking cessation and medication use), can be dramatic.
The American Heart Association Scientific Statement titled ‘Exercise and Physical Activity in the Prevention and Treatment of Atherosclerotic Cardiovascular Disease: A Statement From the Council on Clinical Cardiology (Subcommittee on Exercise, Rehabilitation, and Prevention) and the Council on Nutrition, Physical Activity, and Metabolism (Subcommittee on Physical Activity) published in the journal Circulation in Jun 2003, confirmed that exercise is associated with ~30% benefit in terms of decreased cardiac risk, a magnitude similar to that associated with antihypertensive and lipid-lowering interventions.
However, a study titled ‘Physical Activity and Reduced Risk of Cardiovascular Events: Potential Mediating Mechanisms’ published in the journal Circulation in Nov 2007 found that modification of traditional risk factors fails to fully explain the magnitude of exercise-mediated risk reduction. Based on an analysis of 27,000 subjects, the study reported that differences in known risk factors explained 59% of the cardiovascular disease risk reduction associated with exercise. Blood pressure and inflammatory/hemostatic markers were responsible for the major contributions to exercise-mediated risk reduction, while lipids, body mass index and glycated haemoglobin (HbA1c) contributed to a lesser degree. This statistical modelling suggested that at least 40% of the risk reduction associated with exercise cannot be explained by established risk factors. Beyond the effect on traditional risk factors, exercise has several other benefits on cardiovascular health. These include:
1. Improves vasculature and myocardial perfusion
A study titled ‘Exercise and cardiovascular risk reduction: Time to update the rationale for exercise? published in the Journal of Applied Physiology in Aug 2008 proposed that there are direct effects of exercise on the vascular wall, which confer cardioprotection via a “vascular conditioning” effect. The endothelium produces numerous paracrine hormones, including nitric oxide (NO) which are anti-atherogenic (that protects against atherogenesis, the formation of atheromas [plaques] in arteries). Endothelial dysfunction (discussed in detail elsewhere in the text) precedes and predicts the development of atherosclerotic disease; coronary and peripheral endothelial dysfunction predicts cardiovascular events, and improvement in endothelial function improves prognosis. Exercise increases the intensity of physiological shear stress, inducing changes that result in the production of NO which causes vasodilation, inhibits platelet aggregation and prevents leukocyte adhesion to vessel walls, thus reducing the onset of atherosclerosis, thrombosis, ischemia or other cardiac events.
Besides, another study titled ‘Effects of Exercise to Improve Cardiovascular Health’ published in the journal Frontiers in Cardiovascular Medicine in Jun 2019, suggested that exercise also induces angiogenesis (the development of new blood vessels), however, the mechanisms regulating this process are unclear. It has been hypothesised that the increase in NO production after exercise up-regulates pro-angiogenic (that promotes angiogenesis) factors, particularly vascular endothelial growth factor (VEGF). As a result of the above changes, exercise improves oxygen delivery throughout the body through vasodilation and angiogenesis, protecting against ischemia-reperfusion injury in the heart, thus decreasing the possibility of a cardiac event.
Clinical relevance of direct effects of exercise training on the vasculature
A study titled ‘Percutaneous Coronary Angioplasty Compared With Exercise Training in Patients With Stable Coronary Artery Disease: A Randomized Trial’ published in the journal Circulation in Mar 2004 compared the effects of stenting to exercise training. The study found that after 12 months, the ‘stent group’ exhibited decreased stenosis diameter (81 to 12%), whereas exercise training had no impact (78 to 77%). Nonetheless, significantly higher event-free survival occurred with exercise training (88 vs. 70%). This result is not surprising considering that any coronary intervention can only treat a short segment of the coronary tree, without affecting the progression of coronary atherosclerosis in the remaining vessels. Exercise training with increased shear stress, on the other side, exerts beneficial effects on endothelial function and disease progression in the whole arterial bed. Thus, in contrast, to exercise training interventional cardiology represents palliative care with respect to the underlying atherosclerotic disease process.
2. Heart rate variability and vascular adaptation
Heart rate is the number of heartbeats per minute. Heart rate variability (HRV) is the physiological phenomenon of variation in the time interval between consecutive heartbeats called inter-beat intervals (IBIs). It is measured by the variation in the beat-to-beat (RR) interval. It is also known as ‘RR variability’ and ‘heart period variability.’ A healthy heart is not a metronome (a device that produces an audible click or another sound at a regular interval that can be set by the user, typically in beats per minute [BPM]). The oscillations of a healthy heart are complex and constantly changing, which allow the cardiovascular system to rapidly adjust to sudden physical and psychological challenges to homeostasis. An optimal level of HRV is associated with health and self-regulatory capacity, and adaptability or resilience. It provides indirect insight into autonomic nervous system tone and has a well-established role as a marker of cardiovascular risk. HRV is influenced by various physiological and pathological conditions. Physical inactivity and low resting HRV are associated with increased coronary heart disease incidence.
A study titled ‘Reduced heart rate variability and mortality risk in an elderly cohort. The Framingham Heart Study’ published in the journal Circulation in Aug 1994 demonstrated that low heart rate variability is an independent predictor of cardiovascular mortality. A study titled ‘Effects of moderate and vigorous physical activity on heart rate variability in a British study of civil servants’ published in the American Journal of Epidemiology in July 2003, examined the strength of the Association of moderate and vigorous activity with higher HRV. The study found that moderate and vigorous activity was associated with higher HRV, representing a possible mechanism by which physical activity reduces the risk of coronary heart disease. However, higher HRV is not always better since some pathological conditions, such as cardiac conduction abnormalities, can produce HRV.
3. Mitochondrial biogenesis and improved function
Many of the benefits sustained by exercise are due to adaptations in the mitochondria (the powerhouse of the cell) throughout the body. Mitochondrial biogenesis can be defined as the growth and division of pre-existing mitochondria. According to the study ‘Effects of Exercise to Improve Cardiovascular Health’, referred to above, exercise increases mitochondrial biogenesis in adipocytes, skeletal muscle myocytes, and cardiomyocytes, increasing aerobic respiration within these tissues. Exercise also increases the ability of the mitochondria to oxidise fatty acids (the predominant substrate utilised in healthy myocardium), thus increasing the capacity for ATP synthesis.
A review article titled ‘Defective mitochondrial biogenesis: a hallmark of the high cardiovascular risk in the metabolic syndrome? published in the journal Circulation Research in Mar 2007 suggested that alterations in mitochondrial biogenesis and energetics of cardiomyocytes are linked to the development and progression of cardiovascular disease and heart failure in obesity. Therefore exercise-induced enhancement of mitochondrial function discussed above is important in preventing cardiovascular dysfunction often caused by obesity.
4. Reduction in chronic inflammation
Chronic low-grade inflammation known as inflammaging is associated with multiple diseases including CVD. Exercise, however, results in a long-term anti-inflammatory effect.
In my post, Does obesity hit a point of no return? I had discussed the prospects of long-term success in weight loss maintenance. In the backdrop of the difficulties in maintaining weight loss, I had suggested that emphasis should be on measuring metabolic health and NOT weight. As has been highlighted above, maintaining moderate to high levels of physical fitness improves metabolic health and reduces the risk of various co-morbidities associated with obesity, even if it does not result in any significant weight loss. Therefore increased attention needs to be placed on strategies to maintain or improve fitness in persons with obesity, i.e. though fat but fit.