THE FAT YOU CAN'T SEE: WHAT SCIENCE SAYS ABOUT TRAINING FOR LONGEVITY

GENXJACK | BODY

By Jack Gattenio, M.Ed.

Strength training builds muscle. Cardiovascular training strengthens the engine. The science suggests we need both.

NOT ALL BODY FAT IS CREATED EQUAL

When most people think about losing body fat, they think about what they can see in the mirror. They look at their stomach, their waistline, or the number on the scale, often using those measurements to determine whether their exercise program is working. Unfortunately, appearance and body weight don't always provide an accurate picture of what's happening inside the body. Some of the fat that matters most to our long-term health isn't necessarily visible, and losing weight doesn't automatically mean we're improving every aspect of our physical condition. Understanding the difference between the types of fat our bodies store can help us make better decisions about how we train, particularly as we get older.

One of those types is called visceral fat, and unlike subcutaneous fat, which sits directly beneath the skin, visceral fat accumulates deep inside the abdominal cavity around internal organs. While a certain amount of visceral fat is normal and serves biological functions, excessive accumulation is associated with insulin resistance, cardiovascular disease, type 2 diabetes, and other metabolic health problems. It's possible to have considerable muscle mass and still carry an unhealthy amount of visceral fat, which means looking strong and being metabolically healthy aren't necessarily the same thing. This distinction becomes particularly important for people who have spent years concentrating primarily on resistance training while giving relatively little attention to cardiovascular conditioning. The question, then, isn't simply how we lose weight or build muscle, but how we develop an exercise program that improves our overall health while preserving the strength and physical capability we've worked to establish.

WHAT THE RESEARCH TELLS US

In a discussion about exercise and visceral fat, Dr. Rhonda Patrick explained that aerobic exercise and high-intensity interval training can be particularly effective at reducing fat stored around the internal organs. She also emphasized that resistance training remains essential, especially as we age, but it doesn't necessarily produce the same visceral-fat reductions as aerobic conditioning. That distinction is important because many people assume that any demanding workout must produce essentially the same physiological benefits. In reality, different forms of exercise create different demands on the body, and those demands influence the adaptations we experience over time. Understanding those differences allows us to organize our training around specific goals rather than assuming that working harder at one activity will automatically improve every component of fitness.

A 2026 systematic review and network meta-analysis examined 60 randomized controlled trials involving 3,308 adults with overweight or obesity. Researchers compared aerobic exercise, resistance training, high-intensity interval training (HIIT), and programs combining aerobic and resistance training. All four approaches reduced visceral fat compared with control conditions, but HIIT ranked highest for effectiveness, followed by combined aerobic and resistance training, traditional aerobic exercise, and resistance training alone. These findings are encouraging, although the studies included different populations, training protocols, exercise volumes, and intensity levels, which means the rankings shouldn't be interpreted as proof that one approach is superior for every individual. What the research does suggest is that cardiovascular conditioning deserves serious consideration in a training program designed to improve metabolic health, even when resistance training remains the foundation of that program.

STRENGTH TRAINING IS STILL ESSENTIAL

I've spent decades in gyms, and I've always believed that resistance training is one of the most valuable things we can do for ourselves. Muscle isn't simply something that makes us look better in a T-shirt or gives us the ability to lift heavier weights. It's functional tissue that helps us move, maintain independence, regulate blood glucose, and handle the physical demands of everyday life. As we get older, maintaining muscle becomes increasingly important because the gradual loss of strength can affect balance, mobility, confidence, and our ability to perform ordinary tasks without assistance. Resistance training provides a powerful stimulus for preserving and developing that muscle, making it an important part of healthy aging regardless of whether someone's primary goal is improved appearance, athletic performance, or long-term independence.

A 2025 systematic review comparing aerobic, resistance, and combined training found that aerobic and combined training generally produced greater reductions in absolute fat mass than resistance training alone, while resistance training offered important benefits for preserving fat-free mass. That distinction matters because the number on the scale doesn't tell us how much of the weight being lost comes from fat, muscle, water, or other components of body mass. Someone can lose a considerable amount of weight while simultaneously losing muscle that would have helped maintain strength, mobility, and metabolic function. Conversely, someone who begins resistance training may improve body composition without experiencing dramatic changes in total body weight, particularly when muscle is being developed or preserved. The goal shouldn't simply be to weigh less; it should be to reduce excess body fat while maintaining the muscle that allows us to remain physically capable.

THE CASE FOR HIGH-INTENSITY INTERVAL TRAINING

High-intensity interval training alternates periods of demanding exercise with periods of recovery, creating repeated opportunities to challenge the cardiovascular system. The structure can vary considerably depending on the activity, the person's conditioning, and the intended training outcome. One program might alternate a minute of hard cycling with a minute of easier pedaling, while another might use shorter work intervals, such as 20 seconds of intense effort followed by 10 seconds of recovery. Although these approaches share the general principle of alternating effort and recovery, they don't necessarily produce identical physiological demands or training adaptations. The important distinction is that HIIT is defined by the intensity of the work and the organization of recovery periods, not simply by moving quickly between exercises or completing a workout in a short amount of time.

Research suggests that HIIT can be an efficient way to improve cardiovascular fitness and reduce visceral fat, making it an attractive option for people who have limited time available for exercise. Some studies indicate that meaningful improvements can occur with relatively modest amounts of weekly interval training, particularly when the exercise is performed at sufficiently challenging intensities. However, HIIT isn't magic, and it isn't necessarily superior to continuous aerobic training when workloads are comparable. Higher-intensity exercise also creates greater demands on the body, which means appropriate progression and recovery become especially important for people who are inexperienced, deconditioned, or managing physical limitations. The objective isn't to make every workout as difficult as possible; it's to create an appropriate training stimulus that produces improvement without compromising the ability to train consistently.

For someone who hasn't exercised regularly in several years, beginning with brisk walking, moderate cycling, or another manageable aerobic activity may be more appropriate than immediately attempting demanding intervals. A person with an established conditioning foundation, on the other hand, may be able to incorporate structured intervals into an existing program without sacrificing recovery or performance. Even experienced exercisers should recognize that more intensity doesn't automatically produce better results, particularly when difficult sessions begin interfering with resistance training or other physical activities. The appropriate amount of high-intensity work depends on several factors, including training history, current fitness, age, health, and the demands of the rest of the program. Ultimately, the most effective approach is one that challenges the individual appropriately while allowing enough recovery to maintain consistent participation over time.

WHERE CIRCUIT TRAINING FITS

This is where I find the conversation particularly interesting because circuit training offers an opportunity to combine several important aspects of physical fitness within a single workout. Traditional resistance training often involves completing a set, resting for a designated period, and repeating the exercise before moving to another movement. That approach is effective for developing strength and muscle, especially when the program includes progressive increases in resistance and sufficient recovery between demanding sets. Circuit training organizes the workout differently by arranging several exercises into a sequence, typically with shorter rest periods between movements. Depending on the exercises selected, the resistance used, and the amount of recovery allowed, a circuit can challenge muscular endurance while also creating a meaningful cardiovascular demand.

Consider a circuit that combines a pushing movement, a pulling movement, a lower-body exercise, and a core exercise. Rather than resting several minutes after every set, the individual moves through the sequence with manageable recovery periods before beginning another round. Because different muscle groups are being emphasized throughout the circuit, some local muscular recovery can occur even while the person continues exercising. At the same time, the accumulated effort may keep heart rate elevated and increase the overall conditioning demands of the session. This structure can be particularly useful for people who want to maintain resistance training while incorporating additional conditioning into a limited amount of available exercise time.

However, an important scientific distinction needs to be made before assuming that circuit training produces the same benefits as formal high-intensity interval training. A resistance circuit might provide an excellent conditioning stimulus without reaching the cardiovascular intensity used in controlled HIIT research involving cycling, running, or other aerobic activities. Likewise, an elevated heart rate during resistance training doesn't necessarily mean the body is experiencing the same physiological demands associated with sustained aerobic exercise. We therefore cannot assume that every circuit produces the same visceral-fat reductions observed in studies of other exercise protocols. What we can reasonably conclude is that properly designed circuits offer a practical way to combine resistance exercise with cardiovascular demands, making them a useful option within a broader fitness program rather than a guaranteed substitute for dedicated aerobic conditioning.

THE IMPORTANCE OF TRAINING AS WE AGE

Aging changes the way our bodies respond to exercise, recover from physical stress, and distribute body fat, which makes thoughtful programming increasingly important. Hormonal changes can influence where fat accumulates, particularly around the abdomen, although the relationship between hormones and body composition is more complicated than any single explanation might suggest. Men may experience changes associated with declining testosterone, while women often experience shifts in fat distribution during and after menopause as estrogen levels change. These changes can contribute to an increased tendency to accumulate abdominal fat, but they don't mean that gaining visceral fat is inevitable or that meaningful improvements are no longer possible. Regular physical activity, appropriate nutrition, adequate recovery, and the preservation of muscle mass remain important tools for supporting metabolic health throughout adulthood.

Both resistance training and aerobic exercise can improve important aspects of metabolic health, but they do so through partially different mechanisms. Resistance training helps preserve muscle and can improve glucose regulation and insulin sensitivity, while aerobic exercise improves cardiorespiratory fitness and contributes to reductions in visceral fat. Combining these activities allows us to address multiple components of health without expecting one training method to accomplish everything. Someone who enjoys lifting weights doesn't need to abandon the weight room and become a distance runner, just as someone who enjoys cycling or swimming doesn't need to stop those activities to pursue an elaborate bodybuilding program. The objective is to recognize what each form of exercise contributes and organize our training so that strength, cardiovascular conditioning, and metabolic health support one another.

HOW MUCH EXERCISE DO WE ACTUALLY NEED?

The general adult physical activity guidelines recommend 150 to 300 minutes of moderate-intensity aerobic activity per week, or 75 to 150 minutes of vigorous activity, along with muscle-strengthening activities on at least two days. Those recommendations provide a useful framework for organizing a balanced training program, but they shouldn't discourage someone who is currently doing considerably less. Physical activity doesn't suddenly become beneficial only after a person reaches a particular weekly total, and improvements can begin as someone gradually increases activity from a sedentary starting point. A large 2024 meta-analysis involving 116 randomized trials found that increasing moderate-to-vigorous aerobic exercise was associated with improvements in body weight, waist circumference, and body fat, with approximately 150 minutes per week associated with clinically meaningful improvements in several measures of body composition. The broader lesson is that regular aerobic activity matters, and building toward an appropriate weekly amount can be more productive than attempting an overly ambitious program that becomes difficult to maintain.

For someone who already lifts weights several days each week, incorporating cardiovascular conditioning doesn't necessarily require a complete restructuring of the training schedule. The additional activity might consist of brisk walks on nonlifting days, moderate cycling after selected workouts, swimming sessions, or carefully structured intervals when appropriate. Someone who prefers circuit training may be able to incorporate a conditioning component into existing resistance sessions, although dedicated aerobic activity may still be useful for developing cardiovascular fitness. The important consideration is how the different activities fit together and whether the total training demand allows for adequate recovery. A successful program should reflect the person's goals, available time, current conditioning, and ability to maintain the schedule rather than simply accumulating as many minutes of exercise as possible.

A PRACTICAL APPROACH

If I were building a balanced training week around strength, cardiovascular conditioning, and long-term health, I would begin by making resistance training a consistent priority. For many adults, two to four weekly resistance-training sessions can provide opportunities to challenge the major muscle groups, depending on training experience, recovery, and individual goals. The program should include appropriate exercises, manageable progression, and enough recovery to allow continued improvement rather than repeated exhaustion. Once that foundation is established, I would look for opportunities to incorporate aerobic conditioning through activities the person enjoys and can realistically maintain. Walking, cycling, swimming, rowing, and similar activities can complement resistance training without requiring the individual to abandon the exercises or training routines they already value.

For individuals who have developed an adequate conditioning foundation, one or two carefully structured interval sessions may offer another useful training option. Those sessions don't need to be excessively long, and they shouldn't be programmed without considering the demands of resistance training and other physical activities. Some people may prefer separate cardio sessions, while others may enjoy combining different training methods within the same workout or using circuits for selected training days. People with cardiovascular conditions, significant joint limitations, or long periods of inactivity should seek appropriate medical guidance before beginning vigorous interval training. The goal is to develop a program that fits the individual, creates meaningful physical adaptations, and remains practical enough to follow over months and years rather than simply producing an impressive workout on a single afternoon.

CONSISTENCY BEATS THE PERFECT PROGRAM

One of the most important points in the discussion with Dr. Patrick had relatively little to do with choosing between high-intensity intervals and steady-state cardiovascular exercise. It was about consistency, which remains one of the most important and frequently overlooked elements of physical fitness. Exercise produces lasting benefits through repeated participation, and a demanding workout completed occasionally cannot replace the adaptations created by months and years of regular training. I've watched fitness trends come and go, and I've seen people pursue complicated programs, expensive equipment, and promises of rapid transformation while overlooking the value of simply maintaining a reasonable training schedule. A program doesn't need to be fashionable, complicated, or physically exhausting to be effective, but it does need to provide an appropriate stimulus and be performed consistently enough for the body to adapt.

That doesn't mean every workout will be perfect or that progress will always occur at the same rate. There will be weeks when work, family responsibilities, illness, travel, or ordinary fatigue require adjustments to the training schedule. Those interruptions don't have to become reasons for abandoning the program, particularly when the individual understands that long-term consistency matters more than any single missed workout. The objective should be to develop habits that make physical activity a normal part of life rather than an occasional response to dissatisfaction with appearance or body weight. Train your muscles, challenge your cardiovascular system, recover appropriately, and keep showing up, because the benefits of exercise are built through repetition rather than occasional bursts of enthusiasm.

THE GENXJACK PERSPECTIVE

For me, training has never been exclusively about appearance, even though physical appearance is often what initially motivates people to enter a gym. I've always been interested in what the human body can do and how maintaining physical capability influences the quality of our lives. I want to preserve the strength to perform ordinary tasks without assistance, participate in activities I enjoy, and continue challenging myself physically as I get older. I also want the people I train to understand that exercise should prepare them for life outside the gym rather than simply improve their performance inside it. Strength, mobility, cardiovascular endurance, and metabolic health all contribute to that objective, and neglecting one of those areas can eventually limit the benefits we gain from the others.

The research on visceral fat reminds us that physical fitness has multiple dimensions, and no single measurement or training method tells the entire story. Strength matters because muscle supports movement, independence, and metabolic function, while cardiovascular conditioning matters because the heart, lungs, and circulatory system must be capable of meeting the body's demands. Metabolic health matters because the consequences of excess visceral fat may not be apparent in the mirror or reflected accurately by the number on the scale. We shouldn't sacrifice one aspect of fitness simply because we've become comfortable focusing on another, nor should we assume that getting older means accepting a steady decline in our physical capabilities. The goal isn't to train like we're twenty years old again, but to make informed decisions about what our bodies need today and what we want them to be capable of tomorrow.

Build muscle. Strengthen the engine. Protect your health. Become more capable. Those ideas aren't competing objectives, and the research increasingly supports the value of addressing them together through a balanced exercise program. We can appreciate the benefits of resistance training while recognizing that cardiovascular conditioning deserves a place in our routines. We can use challenging intervals when appropriate without pretending that every workout needs to leave us exhausted. And we can continue learning from the science while remembering that knowledge becomes valuable only when we apply it consistently. That's a training philosophy worth keeping, regardless of how old we get or how many new exercise trends appear along the way.

GENXJACK | BODY

For the professional cool kid.

SHOW UP. KEEP YOUR WORD. DO GOOD WORK. BECOME MORE CAPABLE.

RESEARCH AND FURTHER READING

Optimal exercise modality and dose for reducing visceral adipose tissue in overweight or obese adults: A network meta-analysis and dose-response study (2026). PubMed

Chen et al. Effects of various exercise types on visceral adipose tissue in individuals with overweight and obesity (2024). PubMed

Comparison of concurrent, resistance, or aerobic training on body fat loss (2025). Full study

Aerobic Exercise and Weight Loss in Adults: A Systematic Review and Dose-Response Meta-Analysis (2024). Full study

Dr. Rhonda Patrick and Thomas DeLauer. Scientists Discovered the Best Type of Exercise for Burning Visceral Fat. YouTube interview

This article is intended for educational purposes. Exercise programming should account for individual health, conditioning, and physical limitations.