From women's “golden waist-to-hip ratio” to men's “double-door waist ratio,” what ignites young people's fitness passion often stems from a single number or body type. Today, the latest driving force for fitness enthusiasts is called “low body fat percentage.” On social media, perfect physiques paired with under 20% body fat have become the new narrative for influencers' fitness goals.

Low body fat percentage has become the sole public obsession for fitness physiques. Yet using it as the sole criterion for evaluating a good physique carries significant misconceptions. Low body fat typically indicates a relatively small proportion of fat in the body. This can manifest as low fat but also low muscle mass, or as a lean figure with a lingering belly—especially common among women over 40.

It's unnecessary for the average person to chase after female body fat rates below 20% or male rates approaching 10%. Even male athletes typically maintain average body fat rates between 10% and 11%. Therefore, the public's evaluation of physique shouldn't be confined to a single number. Low body fat doesn't equate to a healthy, aesthetically pleasing physique.

1. When Young People Get Caught Up in Body Fat Percentage “Numbers”

From initial gym assessments to smart home scales, accessing one's body fat percentage has become increasingly easy. Simultaneously, the emphasis placed on this number has far surpassed previous levels. This is especially true for women, whose anxiety about body fat percentage on social media is far more severe than imagined. Posts and comments like:

“What's the most attractive body fat percentage for women?” “Is 23.51% body fat a bit high?” “Reaching 20% feels impossible”—these posts and comments relentlessly pursue lower numbers. Even within healthy ranges, dissatisfaction persists over “love handles” or “back fat.”

Is a body fat percentage below 20% truly necessary for women? On one hand, the Journal of Clinical Nutrition indicates healthy body fat percentages: women aged 20–39 should maintain 21%–32%, while men in the same age group should aim for 8%–19%.

Body composition at different body fat percentages for women Women differ from men in physiological function, requiring higher fat reserves. Typically, maintaining a body fat percentage between 22% and 28% is already a very healthy and natural state. For postmenopausal women, due to declining estrogen levels, fat accumulation around the abdomen is a normal phenomenon. On the other hand, non-professional athletes lack the training and competition demands. For instance, gymnasts require both lightness and strength, typically maintaining body fat between 12% and 16%. Marathon runners, needing sustained endurance and energy supply, often keep their body fat between 14% and 20%. Thus, ordinary women who relentlessly pursue lower body fat percentages are actually adding unnecessary pressure to themselves.

The prevailing societal environment has fostered a trend where lower body fat percentages are idealized, or rather, a state of misinformation, partly fueled by social media's glorification of certain body types.

When low body fat becomes a status symbol for showcasing physique and self-discipline, people tend to overlook its underlying implications. A well-toned physique in bodybuilding isn't achieved because low body fat makes it look good; rather, it's because the physique is well-toned that body fat is low. Rather than fixating on specific numbers, the public needs to understand what body composition ranges correspond to different physiques. This would also prevent absurdities like the widespread misconception that 18% body fat is average.

For example, young women below 18% body fat typically exhibit a more toned physique. Muscle definition begins to emerge, with a flat abdomen potentially showing subtle abdominal lines. The overall appearance is tighter, free from excess fat or flab.

When men approach 10% body fat, six-pack abs typically become visible. At even lower percentages, distinct abdominal separation lines emerge, with higher muscle definition in the chest, arms, and back—sometimes even showing visible veins, especially in the arms and calves.

Of course, preferences vary: some admire the tautness of low body fat, while others liken it to “dried beef jerky.” There is no absolute “ideal physique,” and one should not be confined by body fat percentage figures.

2. Body fat percentage is never the sole standard for evaluating physique

Who would have thought that the body fat percentage you trust so much could also be inaccurate? From measurement methods and equipment to data interpretation, body fat percentage alone cannot fully reflect a person's health status. On one hand, body fat percentage data doesn't accurately reflect muscle mass. Many people use it to gauge fitness progress, especially during muscle-building phases. However, body fat percentage only shows the proportion of fat in total body weight—it doesn't reveal muscle growth.

This means that even if your body fat percentage drops, it doesn't necessarily mean you've gained muscle. You could end up with a very low body fat percentage but also very low muscle mass, resulting in a thin, frail physique.

On the other hand, body fat percentage measurements fail to reveal the specific distribution of fat within the body, yet fat distribution is closely linked to health. Body fat is primarily categorized as subcutaneous fat and visceral fat. Subcutaneous fat is more visible, while visceral fat surrounds internal organs and poses a greater health risk. For example, a “skinny fat” person may appear thin but have a high body fat percentage.

Regarding measurement methods, bioelectrical impedance analysis (BIA) is commonly used. This technique relies on the differing electrical conductivity of body tissues like muscle, water, and fat. However, BIA results are susceptible to factors such as body water content, recent dietary patterns, and post-exercise state. For instance, immediately after exercise, this method may yield a falsely low body fat percentage, creating misleading impressions. For the average woman, pursuing excessively low body fat percentages is inadvisable. Depending on individual differences, levels below 18% may cause menstrual irregularities, while further decreases could lead to amenorrhea. Prolonged estrogen deficiency also impacts bone density, increasing the risk of osteoporosis and fractures.

Moreover, fat serves as a vital energy reserve. When body fat is excessively low, women may experience fatigue, weakness, and diminished athletic performance. Low body fat indicates insufficient fat reserves. If daily caloric intake fails to support physical activity or basal metabolism, the body begins utilizing amino acids from muscle tissue as an energy source, increasing the risk of muscle loss.

Moreover, fat plays a role in regulating immune function. Excessively low fat levels can compromise immunity, making individuals more susceptible to infections. For instance, it's not uncommon to observe fitness enthusiasts who train intensely five times a week and appear highly muscular yet experience frequent colds.

For men, excessively low body fat percentages may lead to decreased testosterone levels. This not only impacts reproductive health but also affects muscle growth, bone density, and muscle mass.

In summary, the ideal body fat percentage varies from person to person. There is no universal standard, and lower isn't necessarily better. For instance, some women experience menstrual irregularities below 22% body fat, while others remain stable below 16%. Some middle-aged or older women fall ill when starting fat loss, while others over 50 maintain low body fat and still run half-marathons. Individual genetics, age, gender, lifestyle, and health status all influence body fat percentage—and vice versa.

3. Don't fall for body fat percentage “marketing”

In an era where short videos captivate us more than traditional knowledge, new metrics periodically emerge as the standard for young people to judge body shape. These fresh standards invariably spark heated debates and trends, becoming the latest buzzwords. From the long-ago “ideal women under 100 pounds” and “A4-waist” trends, these seemingly simple measurements of weight or waist-to-hip ratio actually fueled covert body comparisons and mental constraints. Body fat percentage follows the same pattern. A perfectly normal metric for assessing health has transformed into a number used to flaunt physique and create anxiety.

Attributing body shape and health solely to body fat percentage is inherently one-sided. A truly good physique and healthy body should be evaluated multidimensionally. It depends not only on fat levels but also on muscle mass, waist-to-hip ratio, cardiorespiratory fitness, metabolic health, psychological state, and physical fitness.

Rather than fixating on body fat percentage, it's more valuable to understand whether you have excessive abdominal fat or insufficient muscle mass. In an era where sarcopenia is increasingly affecting younger individuals, focusing solely on fat loss without building muscle is like tearing down fences without building walls. Young women need appropriate levels of fat, but they equally need more muscle. Achieving a good physique requires a multidimensional evaluation—body fat percentage is not the only solution.