Fat loss & Muscle gain

A frequent commenter on my blog, Jme asked the following question:

What if I do not want to lose ANY muscle while trying to lose fat? Then what intensity and duration would be good for me?

This is my answer:

The best way to gain muscle (or prevent muscle loss) is to lift weights. The optimal way to burn calories (lose weight) is to do aerobic activity (but I know you knew that!).

(Because nutrition wasn't part of the question, I'm not going to talk about that today. Suffice to say that macronutrient breakdown doen't change much between exercisers and non-exerciser: ~50% calories from carbs, ~20% from protein and <30%).

There's no research available to predict what percent of weight gain or loss is muscle and how much is fat. The best tool you can use to know you're losing fat and building/maintaining muscle is to have your body composition measured and to re-measure it every 1-3 months. It's a great tool to have to track your progress.

Remember that calipers are not as accurate as bioimpedence measurements (these are the 2 that are more common- there are better methods available though).

Body fat percentage normally changes slightly over time, but only by 1 or 2% over several months.

You have to work to maintain muscle and if you don't work out, your body looses muscle and deposits more fat if you continue to eat the same amount of food.

As for intensity of aerobic activity, it depends on your current fitness level.

A beginner (very low to low level of fitness) can lose weight and improve fitness level by exercising 1-3 times a week at 55-64% of their Max HR*.

A person of average fitness should exercise 3-5 times a week at 65-74% of their Max HR* to see some weight loss and see some improvements in fitness level.

A competitive athlete's goals are generally a bit different in that weight loss is secondary to improving performance (VO2max), competition and training. It's generally recommended that competitive athletes not focus on weight loss too much as that may affect performance.

In order to meet training goals, these athletes should workout 4-7 times a week at 75-90% MaxHR*.

Of course, these are just a general guidelines and can vary depending on training goals and sport.

In terms of resistance training, common goals include wanting to build muscle, muscle definition and to improve overall functional strength and power.

If you want to maintain your muscle mass and develop definition and endurance, it's recommended that you work at an intensity of 70% or less of your 1 RM** (Repetition Maximum- the max amout of resistance you can lift one time) and lift between 12-20 repetitions.

If building muscle is a goal for you, you should be working at ~80% of 1RM** and perform 6-10 reps.

If increasing power is a goal for you, lift at 100% 1RM**!

The more sets you do, the more you fatigue your muscle fibres, the more you encourage muscle growth during the recovery stage. So, if muscle building is a goal for you, use multiple sets. If you're new to lifting weights, current research shows that you can see results with 1 set of each exercise.

Fibre type is also important when talking about resistance training. Slow twitch fibres are the ones that provide most of the movement during low-intensity, long duration activities (50-70% of your 1RM**). To recruit the fast-twitch fibres that that capable of muscle growth, you should exercise with greater force or at higher intensities (>70% of 1 RM**).

Hope this answered your question, Jme!

* To calculate your Target Heart Rate, use the Heart Rate Reserve Method:
Max HR= 220-age

Target HR= {(Max HR-Resting HR) x Range(%) + Resting HR}
Ex. 40 year old with a resting HR of 68 BPM exercising at 60% :
Target HR= {(220-40) – 68 x (0.60) + 68}
Target HR = 135 BPM

** To find your 1RM and % of your 1RM, visit:
http://www.exrx.net/Calculators/OneRepMax.html

Source: Hutton, J. CanFit Pro Personal Trainer Specialist Certification Manual. Toronto: CanFitPro.