While many people worry that they are eating too much and putting on weight, the challenge to physically active exercisers is just the opposite: eating enough to ensure that they perform optimally in their favorite activity. This includes the recreational exerciser to the most competitive athlete, not to mention the hard-working fitness instructors and personal trainers whose workload involves hours of physical exertion.

Why is it important to eat enough ? 

In a single word: PERFORMANCE. That hard-working body of yours uses up energy (those all-important calories) and if you do not replace it, you end up not being able to exercise or play your sport at the level of intensity that you know you are capable of. Apart from your performance going down, you tire more easily and this fatigue starts to get you wondering what you are doing wrong. This may prompt you to start popping pills and supplements in an attempt to re-capture the feeling of energetic strength or endurance, which is both costly and possibly not successful. 

Signs that you may not be eating enough

Undue fatigue while exercising Not being able to exercise as intensely or for as long as usual Feeling like you are not fully recovered from an exercise session before the next session Sense of feeling hungry and in need of sweet food More muscle aches and lethargy than usual

So what do I need to eat & how much of it? 

Let’s talk about energy first. When you exercise, your body uses energy stores in your body. The most readily available store is the sugar in your blood called glucose. This comes from eating carbohydrates. Glucose is also stored in your muscles as something called glycogen. For those of you who participate in endurance activities, it is essential to have those glycogen stores as full as possible before you launch out there for that long run or swim or bike ride.

Other energy stores in the body include fat and, when your body has run out of glucose and fat, your body protein as well. In other words, your muscles. Yes, you can actually start to break down your muscles to supply energy if you do not meet your needs through glucose, glycogen and fat. This is obviously something you do not want to do as it reduces your strength, power and endurance.

So the first thing about eating properly is to eat enough to meet your energy needs.

How do I know what my energy needs are? 

There are very fancy ways to measure your exact energy needs, but these require expensive equipment and quite a bit of time. A more useful way for most of you to measure your energy needs is to calculate them using some formulae. Even if you are not maths-inclined, this is not as difficult as it sounds. Here’s how to go about doing it:

Your energy needs are made up of 2 components: the basic needs for your body just to exist – keeping your heart beating, lungs working, and other body systems running – and this is known as your resting metabolic rate (RMR); and the additional needs arising from your physical activities: working in the office, walking to the bus stop, housework, exercise, sports, etc. So your total energy needs require you to calculate both energy components.

You calculate the RMR using these formulae:

Men	66 + (5 x height in cm) + (13.8 x weight in kg) – (6.8 x age)
Women	655 + (1.8 x height in cm) + (9.6 x weight in kg) – (4.7 x age)

(Why do men need more energy to survive? Well, staying well clear of gender-bias comments, it is generally because men have more muscle mass than women (at any given age or weight). Muscle is more active metabolically which means that it uses up more energy)

As an example, if you are female, 30 years old, weigh 50kg and are 1.5m tall, your RMR is 1264 calories. That’s how many calories you need just to exist. As a point of trivia, this is 12 cans of Coke. Or 2 plates of chicken rice. Or 2.5 Big Macs… (we’ll talk about the fat and protein issues later !!)

Now you have to add on the activities that you do in the day. To do this, you use some simple tables that tell you how much energy is used for every minute spent in your activities. Such tables are available on the internet (example: www. ) and are based on your body weight. Using the table can become very complicated if you calculate every single minute’s worth of activity, so for most of you, a general estimation may be an easier thing to do.

So let’s carry on being that wonderful 30-year woman who weighs 50kg: if the average day’s activity includes walking to the MRT station to go to work come home again (30 minutes), standing in the MRT (40 min), working at a desk (7 hours), walking to/from lunch (20 min), and then the highlight of the day, going for a jog (30 minutes), your activity energy needs would be 1011 calories.

SAMPLE TABLE OF ACTIVITIES (approximate calories expended per minute)

Activity	50kg	60kg	70kg
Badminton Leisure Competitive	4.9 7.3	5.8 8.7	6.8 10.3
Basketball	6.9	8.3	9.6
Bowling	4.8	5.8	6.8
Car washing (manual !!)	3.5	4.2	4.9
Circuit weight training (stacked weights)	5.8	7.0	8.2
Cycling Leisure, 5.5mph Racing > 9.4 mph	3.2   8.5	3.9   10.1	4.4   11.8
Sitting	1.2	1.4	1.6
Golf (non buggy)	4.3	5.1	5.9
Housework	3.4	4.1	4.6
Karate	9.8	11.7	13.6
Running 9 min per mile 7 min per mile 5 min per mile	9.7 12.2 14.5	11.6 14.0 17.4	13.5 16.0 20.2
Soccer	6.8	8.2	9.6
Swimming Breast stroke Free, fast Free, slow	8.1 7.8 6.4	9.7 9.3 7.7	11.4 11.0 9.0
Tennis Recreational Competitive	5.5 7.3	6.5 8.8	7.6 10.1
Walking 3 mph 4 mph	3.8 4.9	4.5 5.8	5.2 6.8

 

Finally, putting it all together (RMR + activity needs) gives you a daily energy need of 2375 calories. While this is a single day’s calculation, it is more practical for you to calculate a weekly total and then try to meet your energy needs by spreading that out over the week. So if you typically take that 30 minute jog on 4 days of the week, and you don’t work on the weekends but add in an hour of swimming and cycling instead, your weekly total would be about 16, 109 alories. So you will need to eat a diet that gives you 2300 calories per day.

Anything else I should consider? 

The source of your energy is in the food you eat, and you will want to try and ensure that about 55-60 % of your energy comes from carbohydrates, 10-15 % from protein and no more than 30 % from fat. But more on this when we look at the diet for active exercisers in our next issue. In the meantime, remember that you are what you eat when it comes to exercise and sports performance. To be the very best that you can be, you can and should eat well. And eat enough to meet the high energy demands of being physically active.