Dr Nick Fuller
Leading Obesity Expert at the University of Sydney and founder of Interval Weight Loss.
It’s hardly shocking that exercise is usually our go-to once we decide it’s time to shed some kilos.
We rush to join the gym, promise ourselves more evening walks, and trust that moving our bodies more will surely make the scales shift.
But after sticking to this for weeks or even months, many people end up frustrated when their weight doesn’t budge. That’s when I often get asked: Is it the workouts that matter, or is diet doing all the heavy lifting?
As with most things about losing weight, the reality is a bit more complex.
Exercise has been studied for decades in relation to weight management. Overall, recent research suggests that exercise by itself has only a modest effect on weight loss. For example, a meta-analysis reviewing multiple studies found that people who relied on exercise alone lost very little weight compared with those who combined exercise with reduced calorie intake.
A 2018 study also highlighted that following the minimum recommended physical activity, that is, 150 minutes of moderate or 75 minutes of vigorous exercise per week, was unlikely to lead to meaningful weight loss. To see significant results without adjusting diet, participants needed to do well above these minimum levels.
In practical terms, research indicates that about 60 minutes of moderate activity per day is generally required for substantial weight loss.
But that doesn’t mean exercise isn’t worth it. Numerous studies confirm that including regular physical activity remains a crucial part of any weight loss program, not only for burning calories but also for overall health, metabolism, and long-term weight management.
Regular exercise not only helps maintain weight loss but also improves body composition and slows muscle loss. Our resting metabolic rate, which is how many calories we burn at rest, is influenced by the balance of muscle and fat in our bodies. Since muscle burns more energy than fat, keeping it is key to sustaining metabolism.
Relying solely on diet to shed kilos can lead to loss of both fat and muscle, which may slow your metabolism. That’s why including adequate and targeted exercise in a weight-loss plan is essential to preserve muscle mass.
Strength-building resistance training is particularly important, but this doesn’t require daily gym sessions. Just two sessions per week, even at home, can be enough. Research shows that moderate-volume resistance training (three sets of 10 reps across eight exercises) is just as effective at maintaining lean muscle as higher-volume routines, especially when paired with a moderately calorie-restricted diet.
Physical activity also plays a major role in preventing weight regain. A longer-term study indicates that individuals maintaining higher levels of exercise, for example, expending over 10,500 kilojoules (around 2,500 calories) per week, such as walking 75 minutes daily, retain significantly more weight loss than those exercising less.
Even before noticeable changes appear on the scales, exercise delivers numerous physical and mental health benefits. Low levels of activity can reduce the risk of conditions, such as heart disease and type 2 diabetes. In fact, exercise can improve many health markers linked to obesity, even without weight loss, making it just as important as losing weight for overall health.
A person with obesity who remains active can maintain good blood pressure, cholesterol, and insulin levels, essentially achieving metabolic health. Evidence shows that moderate-to-high fitness levels can greatly reduce, or even eliminate, the risk of early death associated with obesity.
Beyond these health benefits, regular exercise enhances strength, mobility, mood, and sleep. Even modest activity helps lower stress and depressive symptoms. Improved mood and reduced stress can also support better dietary choices, helping you manage your eating habits more effectively.
Exercise helps burn calories and preserve muscle. But if your metabolism is slow, even workouts may not show results as quickly as you’d expect. To get a sense of what a sluggish metabolism looks like, see 7 Signs You Have a Slow Metabolism for insights that can guide how you combine movement and other strategies.
Exercise is a powerful tool for losing weight and keeping it off, but on its own, it won’t guarantee the results you’re hoping for. It’s one of the core pillars of long-term weight management, working hand in hand with a balanced diet and good sleep habits to support lasting change.
The key is finding activities you genuinely enjoy and mixing things up to prevent boredom. Consistency matters more than intensity. If you stick with it, the benefits compound over time.
At Interval Weight Loss, we combine evidence-based exercise guidance with practical nutrition and lifestyle strategies, helping you create a plan that’s sustainable, enjoyable, and tailored to your goals. Learn more.
Dr Nick Fuller is the founder of Interval Weight Loss and is a leading obesity expert at the University of Sydney with a Ph.D. in Obesity Treatment. Dr Fuller is also the author of three best-selling books and his work been published in top ranked journals in the medical field, including JAMA, Lancet and American Journal of Clinical Nutrition.