What is the Best Exercise for Fat Loss? A Science-Based Guide

The role of exercise in a successful fat loss programme is well established. For example, a review of weight loss interventions found that combining energy restriction with exercise resulted in 20% greater weight loss than energy restriction alone (1).

However, questions remain about the optimal exercise prescription. Traditionally, fat loss programmes have focused on steady-state aerobic exercise. More recently, growing evidence has highlighted the benefits of alternative approaches, particularly high-intensity interval training (HIIT).

So, which approach is most effective?

Fortunately, exercise and fat loss have been the subject of extensive scientific research. In this article, we’ll examine the evidence behind the most popular exercise methods and explain how personal trainers can apply it to create effective fat loss programmes.

Is moderate-intensity cardio still the best option?

Moderate-intensity steady-state aerobic exercise has formed the foundation of fat loss programmes for decades. But how effective is it?

A recent systematic review and meta-analysis of 116 randomised controlled trials involving 6,880 adults with overweight or obesity examined the effects of supervised aerobic exercise on fat loss (2).

The researchers found a clear, linear relationship between the amount of aerobic exercise performed each week and reductions in body weight, body fat, waist circumference and visceral fat.

A minimum of 150 minutes per week was needed to achieve meaningful fat loss, with benefits continuing to increase in a linear, dose-dependent manner up to approximately 300 minutes per week.

For every additional 30 minutes of aerobic exercise performed each week above the minimum threshold:

• Body weight reduced by 0.52 kg
• Waist circumference reduced by 0.56 cm
• Body fat percentage reduced by 0.37%
• Visceral fat area reduced by 1.60 cm²
• Subcutaneous fat area reduced by 1.37 cm²

The findings reinforce current public health recommendations that greater amounts of aerobic exercise generally produce greater reductions in body fat.

Can HIIT burn more fat?

High-intensity interval training (HIIT) has become increasingly popular as a time-efficient method of improving body composition.

HIIT involves repeated bouts of high- to maximal-intensity exercise lasting between 45 and 240 seconds, interspersed with periods of active recovery (5).

A variety of HIIT protocols have been shown to reduce body fat effectively, including:

• 8 seconds work / 12 seconds recovery
• 20–30 seconds all‑out sprints with 2–4 minutes recovery (Sprint Interval Training)
• 30 seconds work / 15 seconds recovery (2:1 ratio)
• 30–60 seconds work / 1–2 minutes recovery
• 2–4 minutes work / 2–4 minutes recovery (longer aerobic intervals)
• Tabata protocol: 20 seconds work / 10 seconds recovery, repeated 8 times (4 minutes total)

How effective is HIIT?

Trapp and colleagues (5) found that 15 weeks of HIIT resulted in:

• Approximately 2.5 kg of fat loss
• Around 2–3 cm reduction in waist circumference
• Significant reductions in visceral fat

Another study (4) found that although endurance training required 48% more energy during exercise, HIIT produced greater fat loss overall. When adjusted for energy expenditure, HIIT was nine times more effective.

Resistance training vs aerobic exercise

Resistance training is now recognised as an important component of fat loss programmes. However, some fitness influencers claim it is superior to aerobic exercise for reducing body fat.

To investigate this, Slentz and colleagues (6) compared aerobic exercise with resistance training.

Aerobic exercise produced the greatest metabolic improvements, including:

• Reductions in visceral, liver, subcutaneous and total abdominal fat
• Improved liver health (ALT)
• Better insulin sensitivity (HOMA-IR)

Resistance training primarily improved body composition by:

• Increasing strength
• Increasing lean muscle mass
• Producing little meaningful reduction in visceral or liver fat
• Having no significant effect on liver enzymes or insulin resistance

Overall, the authors concluded that moderate-volume aerobic exercise remains the most effective and time-efficient strategy for reducing body fat and improving insulin sensitivity.

That said, resistance training remains an essential part of a fat loss programme because it helps preserve lean muscle mass while improving strength and function.

The benefits of metabolic resistance training

Not all forms of resistance training have the same effect on fat loss.

Metabolic resistance training has attracted growing interest because it combines compound exercises with minimal rest periods to maximise energy expenditure during exercise while increasing excess post-exercise oxygen consumption (EPOC). In simple terms, this means the body continues to burn more calories during recovery.

One study found resting metabolic rate remained elevated by 4.7% for up to 38 hours after a training session (7).

Over the course of a year, an 80 kg individual training twice per week could burn an additional 15,000–15,500 kcal during the recovery period alone.

When combined with a calorie-controlled diet, metabolic resistance training has been shown to produce 44% greater reductions in body fat than dietary restriction alone (8).

Is anaerobic exercise better than cardio for fat loss?

Some fitness influencers argue that anaerobic exercise, such as resistance training and HIIT, is superior to traditional cardio. Some have even claimed that aerobic exercise can make you fat.

One argument often presented is that marathon runners are sometimes overweight, whereas sprinters tend to be lean and muscular.

At first glance this may seem convincing, but the comparison doesn’t stand up to closer scrutiny.

Many marathon participants are recreational runners who may have taken up running to lose weight, whereas sprinters are elite athletes who have trained specifically for speed and power.

A more meaningful comparison is between elite endurance athletes and elite sprinters.

Research shows:

• Male sprinters typically have 8–10% body fat, while females have 12–20%
• Male marathon runners generally have 5–11% body fat, with some reported as low as 3.3%
• Female marathon runners typically have 10–15% body fat (9)

A separate 12-week study comparing aerobic and anaerobic exercise (10) found:

• Aerobic training (50 minutes of moderate-intensity exercise, three times per week) produced greater fat loss.
• Anaerobic training (30 minutes of resistance training plus 20 minutes of HIIT, three times per week) produced greater increases in strength and lean muscle mass.

What this means for personal trainers

If we only consider calories burned per minute, HIIT appears to be the superior option. For example, just three 15-second sprints have been shown to expend around 65 kcal, compared with 39 kcal during a 3.5-minute walk (5).

However, fat loss is about much more than simply maximising energy expenditure. Different forms of exercise provide different benefits, meaning there is rarely a one-size-fits-all solution.

Instead, personal trainers should consider each client’s goals, fitness level, health status, preferences and ability to exercise consistently.

For fit, motivated individuals who are short on time, HIIT can be an extremely effective and time-efficient option.

For someone who is overweight, deconditioned or new to exercise, moderate-intensity aerobic exercise performed for longer durations may be a more realistic and sustainable starting point.

Ultimately, the best exercise for fat loss is the one someone can perform consistently over the long term. In practice, the most effective fat loss programmes typically combine multiple training methods to maximise results.

The evidence suggests:

• Aerobic exercise burns more fat during exercise and is particularly effective at reducing visceral fat.
• HIIT provides a highly time-efficient way to increase energy expenditure while also increasing calorie burn after exercise.
• Resistance training may not produce the greatest fat loss on its own, but it is essential for preserving muscle mass, maintaining metabolic health and improving long-term function.

Developing the knowledge to apply these principles is an essential part of becoming an effective personal trainer. If you’re looking to build your expertise in exercise programming, client assessment and evidence-based coaching, explore our Personal Training Course to learn how to design safe, tailored programmes that help clients achieve sustainable fat loss and long-term results.

ACSM Guidelines for Fat Loss

The American College of Sports Medicine (ACSM) provides evidence-based guidelines for adults who are overweight or obese (10). These recommendations provide an excellent framework for beginners while allowing progression for more experienced exercisers.

Aerobic exercise

• Frequency: Five or more days per week
• Intensity: Begin at moderate intensity (40–50% HRR or VO₂R), progressing to vigorous intensity (60% HRR or VO₂R or above)
• Duration: Start with 30 minutes per day (150 minutes per week), progressing to 60 minutes per day (250–300 minutes per week)
• Type: Rhythmic activities involving large muscle groups, such as walking, cycling, rowing, jogging, swimming or using an elliptical trainer

Resistance training

• Frequency: Two to three sessions per week
• Intensity: 60–70% of one-repetition maximum (1RM), progressing as strength improves
• Volume: Two to four sets of 8–12 repetitions for each major muscle group
• Type: Free weights, resistance machines or bodyweight exercises

References

• Curioni CC, and Lourenço PM. Long-term weight loss after diet and exercise: a systematic review. Int J Obes (Lond).2005 Oct;29(10):1168-74.
• Jayedi A, Shab‑Bidar S, Djafarian K. Dose–response association between aerobic exercise and body fat: systematic review and meta‑analysis of randomized controlled trials. Obes Rev. 2024;25(1):e13612.
• Trapp EG, Chisholm DJ, Freund J, Boutcher SH. The effects of high-intensity intermittent exercise training on fat loss and fasting insulin levels of young women. Int J Obes (Lond). 2008 Apr;32(4):684-91. doi: 10.1038/sj.ijo.0803781. Epub 2008 Jan 15. PMID: 18197184.
• Tremblay A, Simoneau JA, Bouchard C. Impact of exercise intensity on body fatness and skeletal muscle metabolism. Metabolism. 1994 Jul;43(7):814-8. doi: 10.1016/0026-0495(94)90259-3. PMID: 8028502
• American College of Sports Medicine. ACSM’s guidelines for exercise testing and prescription. 10th ed. Philadelphia: Wolters Kluwer; 2017.
• Slentz CA, Bateman LA, Willis LH, et al. Effects of aerobic vs resistance training on visceral and liver fat stores in overweight adults: the STRRIDE AT/RT trial. J Appl Physiol. 2011;111(3): 678‑684.
• Schuenke MD, Mikat RP, McBride JM. Effect of an acute period of resistance exercise on excess post-exercise oxygen consumption: implications for body mass management. Eur J Appl Physiol. 2002 Mar;86(5):411-7. doi: 10.1007/s00421-001-0568-y. Epub 2002 Jan 29. PMID: 11882927.
• Kramer WJ, Volek JS, Clark KL, Gordon SE, Puhl SM, Koziris LP, et al. Influence of exercise training on physiological and performance changes with weight loss in men. Med Sci Sports Exerc. 1999;31(9):1320‑9.
• McArdle WD, Katch FI, Katch VL. Exercise physiology: energy, nutrition and human performance. 8th ed. Philadelphia: Wolters Kluwer/Lippincott Williams & Wilkins; 2015.
• Kabir R, Kabir A, Kabir M, et al., Comparative analysis of aerobic and anaerobic exercise on body composition and metabolic health: a randomized controlled trial. 2025;17(2):e78321.
• American College of Sports Medicine. ACSM’s Guidelines for Exercise Testing and Prescription. 12th ed. Philadelphia: Wolters Kluwer; 2025.

Author

Paul Orridge

Paul Orridge BSc (Hons)

Paul Orridge is a graduate in the field of sport, exercise and health, and has over 30 years’ experience within the fitness industry. In this time, he has performed a variety of roles including personal training, lecturing and writing. Paul now works as a freelance technical author and subject matter expert within the fitness industry. His work is based on his practical experience gained working with a diverse range of people from very unfit, overweight individuals to highly conditioned athletes, and is underpinned by the latest research.