This is one of the biggest misconceptions people have about how muscle gain and fat loss works.

Unfortunately, following this misguided information is one of the NUMBER ONE killers of muscle gains!

Weights to build muscle, then cardio to burn the fat (bro!)

It’s true, weights will definitely help you build muscle.

It’s also true that cardio will help you to burn fat.

However, neither of these methods work directly, and if you try to focus on both, you could quite easily be looking at your naked reflection in a year and wondering why it still doesn’t look any different.

Why Shouldn’t you do Weights and Cardio together?

You can do weights and cardio together (well not simultaneously, but in the same session or week), but you need to understand this first:

Cardio does not burn fat directly and it may prevent you from building any muscle.

That’s right, all of those hours you spend on the treadmill are NOT causing the fat cells around your waist to sizzle up and evaporate.

All cardio does is increase the number of calories you burn.

Do cardio for 30 minutes? You might burn 300 – 400 calories. Do cardio for an hour? You might burn 600 – 800 calories.

Notice I said calories, not fat.

Doing cardio does not burn fat. Doing cardio burns calories.

To understand better why using weights to pursue a muscle building goal, and cardio to pursue a fat loss goal at the same time makes no sense, we need to revisit a very important topic:

How does fat loss work?

The only way to “burn” fat, is by being in a calorie deficit.

That means you eat less calories in the day than the amount of calories you burn. This includes the calories you get for free, like the ones your body needs to keep you alive.

If you don’t have any idea what your maintenance calories are, try this calculator from Muscle Hacking.

If you’re a 29 year old male with a lot of lean mass (muscle), you work out hard 4 times a week and have an active job, then you might have a maintenance of 4,000 calories. That means that to lose weight (or “burn” fat) you would have to eat less than 4,000 calories per day on average.

If you’re a 60 year old woman without much muscle, with a job that mostly involves sitting at a desk and you don’t do much exercise, then you might have a maintenance of 1,500 calories. To lose weight, a woman like this would have to eat on average less than 1,500 calories per day.

The bigger the calorie deficit (difference between intake and maintenance) then the faster weight loss will occur.

This is simple science, it always works like this. There’s no arguing with it!

What if You Eat more than Your Maintenance?

If you eat more than your maintenance, quite simply, you will gain weight.

If you’re training hard with weights, sticking to a sensible program and focusing on progressive overload of your muscles over time (getting stronger by lifting more weight or the same weight for more sets and/or reps) then muscle gain will (slowly!) happen.

However, there’s a limit to how much muscle our bodies can build at once. More calories do not equal more gains. Anything extra that our bodies cannot use to build muscle just gets stored as fat.

This is why, when focusing on gaining muscle, it’s important not to shoot straight past your calorie goal and into the distance. “Bulking” is not an excuse to shovel down as much pizza and ice cream as you want. Yes, you can enjoy those things, but you need to be mindful of your total calories. I wouldn’t go more than 20% over your maintenance. 10% is enough.

So Back to the Question About Cardio to Burn Fat

Some people think they can pursue both muscle building and fat loss goals at the same time.

Unfortunately this is not true.

You either need to be in a surplus to build muscle, or in a deficit to lose fat.

Cardio can help you to get into a deficit so you lose fat, increase the size of your deficit so you lose more fat, or reduce the size of your surplus so you gain less muscle or gain less fat. Cardio in itself does not burn fat. You can do all of the cardio in the world, but if you still eat in a surplus you will never lose fat.

And if you are trying to gain muscle, then you need to be in a surplus. Doing cardio to “burn away the fat” only reduces the size of your surplus, possibly eliminating it all together.

Scenario A:

Jim has maintenance calories of 3,000. He wants to gain muscle, so he is eating on average 3,500 calories per day.

Jim is training really hard in the gym, attempting to lift more weight over time.

One day, he thinks that he has a bit more fat than he would like, so he decides he will also try to lose fat by doing cardio. Every day he goes for a run and burns roughly 500 calories on each run.

This results in Jim’s maintenance calories moving up to 3,500. He still only eats 3,500 calories worth of food per day.

One year later, Jim will not have gained any muscle. Nor will he have lost any fat. This is because he has eaten at maintenance which will always result in no weight loss or gain.

Scenario B:

Hayley has maintenance calories of 2,000.

She eats 2,000 calories every day.

She has more fat than she would like, so she decides to do cardio 3 times a week.

Her maintenance calories now move up to average roughly 2,300 calories per day. She does not change what she eats.

She is now eating at a 300 calorie deficit. Over the course of 3 months, this would equate to weight loss of about 3.5 kilograms. At this point, she is happy with her levels of bodyfat, and decides to start eating more and focusing on gaining muscle.

Scenario C:

Brian really wants to lose fat.

He doesn’t realise that it’s calorie balance that really matters. He thinks that cardio and general activity will burn fat directly.

He works his arse off in the gym and goes for a long run every other day. He also starts cycling and swimming.

Before he started, his maintenance calories were 2,500.

After starting all this activity, his maintenance calories are up at 4,000.

Problem is, he’s also getting more hungry because of all this activity. He doesn’t really know how many calories are in foods, but he doesn’t really care. He thinks he’s eating healthily. He eats a lot of salmon, a lot of grass fed beef, eggs, bacon, sausages etc. He drinks a lot of orange juice too for that vitamin C, never realising that he’s getting 400 calories a day from it.

He thinks cutting out carbs is good, and eating high fat foods will make him lose fat. He allows himself a day off each week and often goes out on this day and sinks some beers with the boys.

Brian keeps this up for a year, thinking he’ll surely lose fat because he’s doing so much exercise, and cardio burns fat, right?.

The problem is, Brian is now consuming 4,100 calories per day on average.

After a year, that amounts to a total surplus of 36,500 calories. That will see him almost 5 kilograms heavier than when he started!

Conclusion

Cardio does not burn fat directly.

Cardio only burns calories.

To lose fat you need to be consuming less calories than you’re burning.

To gain muscle, you need to be in a calorie surplus. If you’re serious about gaining muscle, you need to make sure your cardio doesn’t reduce the size of your surplus to non-optimal levels, or wipe it out completely. If it does, say goodbye to any potential gains.