Nutrition for Stripping Fat & Building Lean Muscle Mass for Race Readiness

Last updated: 28-Jun-16

By Diana Green

Does excess body fat stand between you and a faster race? Here, Diana Green, runner and sports nutritionist looks at all the different factors that come into play and gives science-based, practical advice on how to strip fat, build lean muscle and so improve your running performance.

A leaner body composition can result in more efficient and economical movement. Leanness has a significant enough effect on performance that every ultra runner should be monitoring their body fat percentage as closely as they monitor their training.

What is your ideal racing weight and body fat percentage?

The Scientific: Your optimal body fat percentage determines your ideal racing weight. Use body fat scales to measure your current body fat percentage and then compare it against the recommended racing body fat percentage range for your age and gender. Make a realistic prediction based on current body fat percentage and potential for improvement in training and diet.

AGE RANGE 20 – 29 30 -39 40 – 49
Men 3 – 10 % 5 – 12 % 6 – 15 %
Women 10 – 16 % 11 – 17 % 14 – 22 %


The Practical: Genetics, fitness and body weight history will limit your achievable body fat percentage so it is never going to be an exact science. Ultimately it is performance that will show your true ideal racing weight.

How easy is it to strip excess fat?

The Scientific: To achieve a reduction in body fat a state of negative energy must be created. This can be accomplished by increasing energy expenditure or reducing energy intake or a combination of both. In other words simply eating fewer calories than your body requires.

The Practical: It sounds easy, however stripping fat while maintaining muscle mass and maximising performance can be far more difficult. Too great a deficiency in calories can result in glycogen depletion and increased protein oxidation.


The secret to successful fat stripping is to improve fat burning.

What is Fat Burning?

The Scientific: Fat burning is the ability to oxidise fat. A mixture of carbohydrates and fat are used by the muscles as fuel at rest and during exercise. Fat metabolism is thought to be most dominant during low intensity/high volume exercise, carbohydrate metabolism becoming more dominant during more intense exercise. However fat and carbohydrate metabolism cannot be separated even during low intensity exercise carbs are the preferred source of fuel and will therefore be burned alongside fat.

The Practical: Individual metabolism of both fats and carbohydrates can vary hugely. This genetic variation can explain why for some runners just a quick morning cup of coffee before a run is enough while others need a good carbohydrate breakfast. These differences in metabolism will determine which fat burning strategy will work best for you.



The Scientific: Take a VO2 Max test to determine your most efficient fat burning zone i.e at what heart rate you are burning the most fat. 

The Practical: Training results in adaptations to preserve blood glucose and muscle glycogen by becoming more efficient at utilising fats as an energy source.

Research shows that aerobic, high intensity and resistance exercise all have favourable effects on fat oxidation. Therefore by following your personal training programme your body will naturally become more efficient at fat burning.

Balancing Carbohydrates

The Scientific: Excess carbohydrate is converted into glycogen if there is spare storage capacity and if there is only a modest rise in blood sugar levels. If there is consumption of excess carbohydrates to energy requirements and/or a rapid rise in blood sugar levels produced by consumption of high GI carbohydrates this can lead to fat storage.

The Practical: In reality the body is constantly storing and using up fat in varying ratios. After a meal you store more fat and between meals and during exercise you burn more than you store. It is the overall balance between these two processes over several days that dictates body composition. Whether you need to cut your carbohydrate intake to achieve a state of negative energy will depend on your fat loss targets. Finding a carbohydrate balancing strategy that works for you and making good food choices without necessarily changing total calorie intake can be an effective fat burning strategy.


Weekly carbohydrate cycling

Calculate your weekly carbohydrate requirements to include any adjustments to total calorie intake (see article ‘Diet for the Ultra Runner’) and vary your intake according to the level of activity i.e fuel your training sessions but don’t over fuel your rest days. Your daily protein and fat intake should remain constant (see article ‘Diet for the Ultra Runner’ to calculate).

Positives: Carbohydrates will be used as an effective energy source with less storage as fat. By fueling your training sessions you ensure proper glycogen replenishment and performance should remain unaffected. This strategy can also automatically control the intake of carbs without too much careful calculation and even result in a decrease in overall calorie intake if desired.

Negatives: Getting into the habit of eating carbohydrates as a reward for exercise can result in a poor relationship with food and cause both over exercising and binging on unsuitable foods.

Fasted state training

Train in a fasted state e.g first thing in the morning before a meal.

Positives: Training in a fasted state can be an effective way to obtain the highest fat oxidation rates. Carbohydrate intake before exercise will suppress fat oxidation due to the effects of insulin. As well as up regulating fat oxidation the release of adrenalin can improve focus and concentration during training.

Negatives: Some studies show that although higher fat oxidation rates are achieved during exercise in the fasted state there is no overall difference when measured over a 24 hour period. Reduced performance during fasted state training might be experienced.

Intermittent fasting

Intermittent fasting involves going without food for longer than one’s normal night time fast. Fast for 16 hours and eat wit in an 8 hour window. For example your first main meal could be lunch at 12:00 p.m and your second main meal supper before 8:00 p.m.

Positives: Fasting increases the secretion of the stress hormones cortisol and adrenaline which up regulates lypolysis, the release of fatty acids from the fat cells for use as fuel.

Intermittent fasting can be used as a fat loss tool without having to change calorie intake, also it can help adherence to an eating plan by controlling hunger and cravings. Hunger can be habitual, triggered by routine, so changing eating patterns can help control hunger as can having two larger satisfying meals rather than four smaller meals.  Forgetting about food during the ‘don’t eat’ time period can be also be an effective way of eliminating cravings.

Intermittent fasting need not impact on training. Either train fully fueled during the ‘feeding’ hours or during ‘fasting’ hours (see potential advantages of this above).

Negatives: If more than normal amounts of food are consumed during the ‘feeding period’ there will be rapid fat gain which could cancel out the ‘fasting’ period fat loss.

Better carbohydrate choices

Chose nutrient dense unrefined carbohydrates to provide sufficient micronutrients for energy production. For the mitochrondria within our cells to efficiently convert fat into the chemical form of energy Adenosine Tri Phosphate (ATP) micronutrients to include B vitamins and magnesium are essential.

Couscous Quinoa Beans
White rice Brown rice Lentils
White rice noodles Buckwheat noodles Chickpeas
White potatoes Sweet potatoes Pearl Barley
White bread Rye bread Oats
White pasta Spelt pasta Rye & Oat crackers

Positives: Greater intake of micronutrients should result in more efficient fat burning as well as maintaining good health. Nutrient dense carbohydrates have a lower glycemic index (i.e release energy slowly) which controls insulin levels and fat storage.

Negatives: None! However if you find it difficult to give up your refined carbohydrate fast releasing snacks then have them as part of your glycogen replenishment strategy to get your glycogen recovery off to a quick start.

Thermogenic foods

It is claimed that some food have Thermogenic (Fat Burning) qualities.


Caffeine stimulates the sympathetic nervous system resulting in increased heart rate and the release of fatty acids into the blood stream for use as fuel.

Positives: Caffeine can enhance performance, increasing mental alertness, time to fatigue and strength output as well as promoting fatty acid mobilisation. 3 – 5 mg of caffeine per kg of body weight in considered to be the optimum amount with no increase in performance seen at higher doses.

Negatives: The individual effects of caffeine on metabolism are highly variable with fat burning benefits reduced due to tolerance. Negative side effects of caffeine can include anxiety, headaches and insomnia.

Essential fats

Omega 3 polyunsaturated fats found in oily fish, nuts and seeds have been found to up regulate fatty acid metabolism resulting in a shift towards greater use of fat as an energy source and reducing the rate of glycogen depletion.

Positives: Essential fats enhance oxygen delivery to muscles and can result in improved performance. Essential fats also have anti-inflammatory properties which can help control exercise induced inflammation.

Negatives: When self-administering supplements of omega 3 fats to achieve the potential benefits caution must be taken to ensure the body’s balance of omega 3 and omega 6 is maintained.

Tips for success

Manage your Appetite
Make sure that your hunger is tied to your physical needs. When satisfying your hunger, it is easy to consume more than the body actually requires.

Monitor your progress
Recording your progress will ensure awareness of which strategies are working for you and help maintain commitment.

Train for Performance
Your training is a powerful tool for successful fat burning. Training for optimum performance together with nutrition will get the best possible results.

Consume Adequate Carbohydrates
An adequate carbohydrate intake is critical for preserving muscular strength, endurance and a high metabolic rate.

Discover Your Uniqueness
Your metabolism, detoxification and requirement for micronutrients is unique. In the future no doubt genetic research will provide a detailed analysis of self, but meanwhile there is going to be a certain amount of trial and error in discovering what works for you.

For more on Diana, click here.

"Leanness has a significant enough effect on performance that every ultra runner should be monitoring their body fat percentage as closely as they monitor their training"

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Date Range

Global - Virtual


A virtual race which can be run at any time shown on the dates shown, on any type of terrain in any country.

Suitable for

For runners from beginners to experienced as you choose your own course and challenge based on the guidelines and options set by the virtual race organiser.

Endurance - Multi-activity


An ultra distance race including at least two of the following activities such as running, swimming, cycling, kayaking, skiing and climbing. It may also include different climatic conditions (eg ice, snow, humidity, cold water, mud or heat).

Suitable for

Experienced multi-skilled athletes who have trained for the different activities included in this event. Admission to these races may be subject to receipt of a recent medical examination certificate. Check with the race organiser regarding entry requirements and any specialist equipment required such as a wetsuit, skis or a mountain bike.



Increase of up to 2000 metres with very challenging climatic conditions (e.g. ice, snow, humidity, heat or at high altitude)

Suitable for

Very experienced long distance ultra runners (min 3 years’ experience) or are doing regular long distance running (>50 miles) with elevation and conditions shown (where possible). Admission to these races is often subject to receipt of a recent medical examination certificate. Purchase of specialist kit is often recommended for these races.



Increase of up to 2000 metres with some challenging climatic conditions (e.g. ice, snow, humidity or heat)

Suitable for

Experienced runners who have completed at least 4 ultras in last 12 months, or are doing regular long distance running (>50 miles) with elevation and conditions shown (where possible). Admission to these races may be subject to receipt of a recent medical examination certificate. Check with the race organiser regarding entry requirements.



Increase of up to 1500 metres

Suitable for

Runners who have completed several ultra distances or similar events, or are doing long distance running regularly, with elevation shown.



Increase of up to 1000 metres

Suitable for

Runners who have completed at least one ultra in last 6 months or are doing long distance running (>26 miles) regularly, with elevation shown.



Very little change < 500 metres

Suitable for

First ultra event. Runners completing a marathon or doing regular long distance running (>26 miles) in the last 6 months.