So many gym goers are focused on fat loss.
For some, that means adding cardio to boost calorie burn.
But when you look around the gym, you'll see many different kinds of cardio.
So what’s the best type of cardio for fat loss? Let’s take a look at what the research says about some common cardio questions.
How Much Cardio Should I Do?
Large amounts of cardio are common during fat loss. But is this the best approach?
A recent meta-analysis (statistical analysis of multiple studies on the same topic) on cardio found that strength and size gains were reduced as the amount of cardio increased.1 These results suggest that doing as little cardio as possible is likely optimal.
However, doing no cardio during a fat loss phase may not be practical or possible for many of us. So how much cardio should you do to promote fat loss but not interfere with muscle size and strength gains?
To answer this question, we need to first discuss energy balance. Weight is gained when energy consumed exceeds energy burned. Weight is lost when energy burned exceeds energy consumed. To lose weight you need to create a negative energy balance by reducing caloric intake, increasing activity, or a combination of both.
Creating a deficit by only reducing calories can result in some miserably low intakes. However, adding in a bit of cardio may help keep calories a bit higher while dieting and make the experience less miserable.
Therefore, the most optimal amount of cardio for fat loss is the least amount needed (combined with diet) to result in an appropriate rate of fat loss.
What Should I Do For Cardio?
For fat loss, there is no best type of cardio. If you enjoy taking fitness classes to burn extra calories, do that. If you enjoy being outside, by all means do your cardio outdoors. The most important thing is to stay consistent with your cardio protocol and choose types of cardio you enjoy.
That being said, one thing you may want to avoid is doing cardio for a body part prior to lifting that body part.1,2 For example, if you are doing cardio in the morning and lifting legs at night, it may be best to do an upper body/total body form of cardio (e.g. battle ropes or sledgehammer slams). Or, lift in the morning and do cardio at night to keep lifting performance high and hold onto muscle while dieting.
How Hard Should I Be Working During my Cardio Sessions?
It is common to see individuals doing lower intensity cardio to keep their heart rate in the “fat burning zone.” While it is true that a higher percentage of fat is burned during low-intensity cardio, there is no difference in the amount of fat burned over a 24hr period between cardio done in the “fat burning zone” and those training at a higher intensity.3,4 Additional fat loss does not occur with low-intensity cardio in the “fat burning zone.”
In addition, a recent meta-analysis on cardio found that lower intensity cardio negatively affected muscle size and strength gains more than higher intensity cardio.1 Based upon these results, it appears the optimal approach for fat loss is high-intensity cardio.
However, it should be noted that high intensity cardio can be more difficult to recover from, comes with a higher risk of injury, and may impact performance while lifting weights if the amount performed exceeds recovery ability. In addition, those with joint issues may want to limit high-intensity cardio to reduce impact.
As such, it may be best to perform high-intensity cardio if possible. But if doing so interferes with lifting performance and recovery, lower-intensity forms of cardio should also be incorporated.
Should I Do Cardio in the Morning on an Empty Stomach?
Many individuals perform cardio in the morning on an empty stomach because they believe it will result in more fat loss. Turns out this isn’t supported by research, just anecdotal evidence.
Studies examining what is burned during fasted vs. fed-state cardio have shown that there are no differences in the amount of calories burned, but a higher percentage of fat is burned during fasted cardio.5,6
However, if we take a look at what is happening during the hours after exercise, a greater amount of fat is burned following fed-state cardio.6 This means that fasted cardio does not result in a greater amount of fat burned over a 24hr period.
In addition, more amino acids are also burned during and skeletal muscle protein degradation (the rate at which muscle is breaking down) is increased following fasted cardio.7,8 Increased protein and amino acid breakdown is not necessarily a good thing if you are trying to build/conserve muscle while losing fat.
It is also important to look at long-term studies to compare the effects of doing cardio in a fed or fasted state on fat loss.
A recent study by Schoenfeld et al. looked at healthy young adults on a meal plan providing the same caloric deficit and had them perform 1hr of morning cardio 3 times weekly for 1 month. Half of the participants received a protein shake before cardio so they were training in the fed state. The other half received the shake after cardio so they were training in the fasted state.
After 1 month, both groups lost body weight and body fat. However, there were no differences in muscle, fat, or weight loss between groups.
Taken together, these results suggest that there is no difference in performing cardio on an empty stomach or after a meal.9 However, if cardio is performed on an empty stomach, having a protein shake or meal after may help prevent muscle loss.
Related: This Year's Best Protein Powders
- There is no “best” cardio protocol for fat loss. Find something you enjoy doing and incorporate variety to keep things fun.
- Aim to do the least amount of cardio while still seeing appropriate rates of fat loss.
- Perform high-intensity cardio if you can. If you are not able and/or doing so interferes with recovery from lifting weights, do lower-intensity cardio.
- Perform cardio on an empty stomach or after a meal based on preference. If performing fasted cardio, it may be beneficial to have a protein shake or meal after your cardio sessions.
- Wilson, J.M., et al., Concurrent Training: A Meta Analysis Examining Interference of Aerobic and Resistance Exercise. J Strength Cond Res, 2011.
- Helms, E.R., et al., Recommendations for natural bodybuilding contest preparation: resistance and cardiovascular training. J Sports Med Phys Fitness, 2015. 55(3): p. 164-78.
- Melanson, E.L., et al., Effect of exercise intensity on 24-h energy expenditure and nutrient oxidation. J Appl Physiol (1985), 2002. 92(3): p. 1045-52.
- Saris, W.H. and P. Schrauwen, Substrate oxidation differences between high- and low-intensity exercise are compensated over 24 hours in obese men. Int J Obes Relat Metab Disord, 2004. 28(6): p. 759-65.
- Deighton, K., J.C. Zahra, and D.J. Stensel, Appetite, energy intake and resting metabolic responses to 60 min treadmill running performed in a fasted versus a postprandial state. Appetite, 2012. 58(3): p. 946-54.
- Paoli, A., et al., Exercising fasting or fed to enhance fat loss? Influence of food intake on respiratory ratio and excess postexercise oxygen consumption after a bout of endurance training. Int J Sport Nutr Exerc Metab, 2011. 21(1): p. 48-54.
- Lemon, P.W. and J.P. Mullin, Effect of initial muscle glycogen levels on protein catabolism during exercise. J Appl Physiol, 1980. 48(4): p. 624-9.
- Kumar, V., et al., Human muscle protein synthesis and breakdown during and after exercise. J Appl Physiol, 2009. 106(6): p. 2026-39.
- Schoenfeld, B.J., et al., Body composition changes associated with fasted versus non-fasted aerobic exercise. J Int Soc Sports Nutr, 2014. 11(1): p. 54.