- Obesity management guidelines often emphasize weight loss through calorie restriction and increased physical activity.
- Weight reduction is difficult to maintain, and repeated attempts have been linked to negative health effects.
- Increased physical activity and improved fitness levels, even in the absence of weight reduction, can lower the risk of obesity-related health problems and death, according to a recent analysis.
- Obesity management that focuses on boosting fitness rather than weight reduction might be just as successful as weight loss at lowering the negative health effects of obesity.
In 2017–2018, 42.4 percent of people in the United States were obese, up from 30.5 percent in 1999–2000, according to the Centers for Disease Control and Prevention (CDC)Trusted Source.
Obesity rates have risen in tandem with an increase in individuals seeking to reduce weight. However, the calorie restriction required for weight reduction might be difficult to maintain for an extended length of time.
Furthermore, many people are unable to reach their ideal weight, and those who do are frequently unable to maintain it.
According to the Centers for Disease Control and Prevention (CDC)Trusted Source, 42.4 percent of Americans were obese in 2017–2018, up from 30.5 percent in 1999–2000.
Obesity rates have grown in lockstep with the number of people looking to lose weight. The calorie restriction necessary for weight loss, on the other hand, may be difficult to sustain for a lengthy period of time.
Furthermore, many people are unable to achieve and maintain their optimum weight, and those who do are usually unable to do so.
Some experts have suggested during the last two decades that a weight-loss-focused strategy to obesity care may be misguided. Instead, they recommend that those who want to reduce weight focus on a "fat-but-fit" approach that includes increasing physical activity and boosting cardiorespiratory fitness.
Advocates of the fat-but-fit approach to obesity therapy claim that boosting fitness can help lower the risk of cardiovascular disease and mortality even if weight reduction is not achieved.
Now, a study published in the journal iScience examines ways to lower the risk of obesity-related health problems and mortality. It compares the efficacy of physical activity and cardiorespiratory fitness to the success of weight reduction.
According to the data presented in the study, the fat-but-fit method may be just as beneficial as weight reduction in lowering the risk of cardiovascular disease and mortality associated with obesity. Furthermore, by focusing on fitness rather than weight reduction, this technique avoids the problems of the weight loss approach.
The relationship between BMI and mortality risk
Doctors use the body mass index (BMI), which is the ratio of a person's weight to the square of their height, to determine if they are overweight or obese.
People with a BMI of higher than 25 kg/m2 but less than 30 kg/m2 are overweight, whereas those with a BMI of 30 kg/m2 or more are obese, according to the conventional categories.
Although some studies suggest that those with a BMI of more than 25 kg/m2 had a higher risk of death, others contradict these findings, according to the authors of the present study.
According to some of the research, those who have a BMI in the overweight range have a reduced mortality risk than people who have a BMI in the healthy range, which is between 18.5 and 24.9 kg/m2. Furthermore, one of the research found that those who are obese do not have a higher mortality risk than people who are of a ‘healthy’ weight.
Weight loss and the risk of death
While some studies suggest that deliberate weight reduction by calorie restriction and physical activity can lower mortality risk, others show that weight loss and mortality risk are unrelated.
To put it another way, research hasn't consistently proven that losing weight lowers mortality risk.
The most common weight-loss advice is to reduce calorie consumption while increasing physical exercise. As a result, studies indicating a reduction in mortality risk related with weight loss may be attributing this finding to an increase in physical activity rather than weight loss itself.
The authors of the current study also point out that maintaining weight reduction over time might be difficult. Weight cycling has become increasingly common as more people try to reduce weight by lowering their calorie consumption.
Weight cycling is linked to an increased risk of cardiovascular disease-related and all-cause death, according to three recent meta-analyses.
Dr. Glenn Gaesser, an Arizona State University professor and co-author of the study, was questioned by Medical News Today if harmful habits like severe calorie restriction may explain the limited advantages of weight reduction in obese people. According to Dr. Gaesser:
Risk of mortality and fitness
Unlike weight reduction, there is greater evidence that cardiorespiratory fitness can significantly reduce or even eliminate the mortality risks associated with a high BMI.
According to a Trusted Source meta-analysis, cardiorespiratory fitness can considerably lower the risk of all-cause and cardiovascular disease-related mortality linked with a high BMI. Furthermore, fit people with excess body weight had a reduced risk of death from any cause than unfit people with a healthy weight.
Physical exercise can also reduce the risk of all-cause and cardiovascular disease-related mortality that comes with a high BMI. Physical activity, on the other hand, has a smaller influence on mortality risk than cardiorespiratory fitness.
Increased physical activity and improved cardiorespiratory fitness can also lower the mortality risk linked with BMI in the long run, according to follow-up studies.
Furthermore, gains in cardiorespiratory fitness and physical activity are associated with a lower risk of death than weight loss.
Notably, several of these studies found that the benefits of physical exercise and enhanced cardiorespiratory fitness were accompanied with either minor or no weight reduction. This means that the lower all-cause and cardiovascular disease-related mortality risk linked with better exercise cannot be attributed to weight reduction.
Markers of cardiometabolic health
Improvements in indicators for obesity-related illnesses, such as cardiovascular disease and type 2 diabetes, can also be achieved by increased physical activity and cardiorespiratory fitness. These changes in cardiometabolic indicators are similar to those seen with weight reduction.
According to the authors of the current study, both resistance training and aerobic exercise lower blood pressure, with the magnitude of the drop comparable to that seen with weight loss.
Similar to weight reduction, exercise training increases blood glucose management, blood cholesterol levels, and vascular function. Weight reduction had no influence on the benefits of exercise training on the aforementioned cardiometabolic indicators.
Exercise training can also help you lose weight by lowering the amount of fat you store in your liver and visceral adipose tissue. The fat that surrounds internal organs, particularly in the belly, is known as visceral adipose tissue.
The fat reserves in the liver and visceral adipose tissue are linked to an elevated risk of cardiovascular disease and type 2 diabetes, according to research.
While the amount of fat stored in the liver and visceral adipose tissue tends to correspond with the amount of weight lost, exercise training can result in a clinically meaningful reduction in fat storage in the liver and visceral adipose tissue even if weight loss is not achieved.
While extreme calorie restriction is more successful than exercise training in decreasing fat storage, the authors point out that calorie restriction for lengthy periods of time is not typically sustainable.
Reduced insulin sensitivity of fat tissue occurs in obesity and type 2 diabetes, and exercise training can enhance fat tissue's responsiveness to insulin.
Implications
For obesity management, the authors propose a weight-neutral strategy that focuses on improving cardiorespiratory fitness and boosting physical activity.
While healthcare practitioners should not discourage weight loss, it should not be the major emphasis of obesity management, according to the authors.
“Current obesity treatment guidelines do not even mention ‘fitness,' and simply urge physical exercise as a method to help weight loss,” Dr. Gaesser explained. This strategy ignores the significant reductions in mortality and disease risk linked with increased physical activity and fitness even when weight loss is not achieved. In fact, compared to weight loss, improved fitness through increased physical activity is associated with larger decreases in mortality risk.“
“Fitness should be considered an important ‘vital indicator' when measuring a person's health. Although this analysis focuses on obesity, it is crucial to note that exercise has an influence on everyone's health and lifespan prospects, independent of body weight,” Dr. Gaesser noted.
Challenges
Dr. Jennifer Kuk, an associate professor at York University in Canada, spoke with MNT about the difficulties in determining the specific impact of fitness in obesity-related health problems.
“Unlike body weight, which is a relatively easy metric that is often commonly done by self-report,” Dr. Kuk explained, “fitness requires an exercise test, the gold standard of which is a maximum activity test.” For both the researcher and the volunteer, this is costly [and] time- and labor-intensive.”
“Physical activity is frequently reported through self-report, although the links between activity and health are not always as strong as those seen with fitness. Physical activity and fitness do not necessarily correlate since there is a genetic component that determines your capacity to improve your fitness via exercise. Furthermore, self-report difficulties may contain recollection mistakes, making it more difficult to discern the real link between exercise and health.”
The authors of the study and Dr. Kuk both emphasized that only a limited percentage of people may be classified as obese yet fit, making it difficult to examine the link between fitness and obesity-related health problems. There are also issues with the absence of defined standards for determining whether a person with a certain BMI and fitness test result (VO2 max) is fit or unfit.
“[Another] concern is that there might be a reverse causality impact with physical exercise and fitness. Is your fitness or activity level a reflection of your health or the other way around (i.e., you are less active and fit because you are sick vs. you become sick because you are less active and fit)?, Dr. Kuk asked.
“This is especially noteworthy considering that even moderate quantities of physical activity, sometimes considerably lower than what is suggested in the physical activity guidelines, are linked with the greatest reductions in mortality risk.”
Qualifications and caveats
The necessity of raising fitness levels for the management of obesity, as recommended by the fat-but-fit strategy, is well acknowledged. However, the scientific and medical communities are concerned about the focus placed on weight loss and other obesity-related issues.
“Physical exercise has been demonstrated to benefit health independent of weight loss,” Dr. Jennifer Bea, who promotes a sophisticated, multidimensional approach to obesity management, told MNT. Improved body composition, i.e., increased skeletal muscle mass and decreased adipose tissue, is one way that physical exercise impacts cardiometabolic health.”
“BMI, which is used in the United States and other countries to diagnose overweight and obesity, is not a direct measure of body composition [...] Physical activity, of course, increases cardiovascular fitness, which reduces risk.”
“We must not forget about those who are deemed normal weight,” Dr. Bea continued. Poor body composition has also been linked to poor cardiometabolic biomarkers and health risks in those with a 'normal BMI.'
“While there is minimal risk in advocating for increased physical activity across weight categories when following the [American College of Sports Medicine (ACSM)] guidelines for physical activity testing and prescription, it would behoove us to move beyond BMI to a more comprehensive evaluation of risk factors that at the very least includes body composition, physical activity, blood pressure, and blood biom,” says the study.
Dr. Bea is a member of the ACSM and an associate professor of medicine at the University of Arizona Health Sciences.
“In the end, I think there is unanimity that fitness and physical exercise are helpful, and obesity is harmful to one's health,” Dr. Kuk said. It's probably not a good idea to concentrate entirely on one element at the expense of the other.”
إرسال تعليق