Metabolism is the sum total of all the chemical reactions that take place within all the cells of the body. These chemical reactions use up energy and of course, the more energy you use up the more fat you will burn. Metabolism is a very individual thing. I'm sure you know some people who can literally eat whatever they want and still lose weight, whilst others only need to look at food and they put weight on.

Why is this? Well, there are 3 major factors that influence our metabolism and we will examine each one to find out how you can affect it using lifestyle factors so your metabolism fires up to the point that your body turns into a 24-hour-a-day fat-burning machine!

Muscle mass

The first factor is your muscle mass. Since muscle is the most metabolically active tissue in the body (along with nerve tissue), which means it burns up the most energy, the more muscle you have, the faster your metabolism gets and the faster you can burn off body fat.

Now I know you're probably thinking, ?But I don't want to put on muscle!? Before you disregard this idea, consider this: If you want to lose weight and you don't force your body to at least maintain your existing muscle mass (through weight training), up to half of the weight you lose can come from muscle tissue. If this occurs, your metabolism will slow down dramatically making it harder to continue to lose weight and easier to put the lost weight back on. This is often the case when people go off a diet, they put the lost weight back on and it usually comes back with re-inforcements! It is called yo-yo dieting, referring to the up and down movements of the dieter's bodyweight.

All you need to do to prevent the muscle loss that results from dieting and/ or performing aerobic exercise is to simply perform a minimum of two 30-minute weight training sessions a week. A qualified personal trainer can show you exactly what to do to ensure you weight train safely and effectively.

Furthermore, if you put on just a few kilos of body-shaping muscle it will have a huge impact on your metabolism. For every kilogram of muscle you put on, your metabolism increases by around 100 calories per day and over a few weeks this can help burn up a substantial amount of body fat. So even though your bodyweight may not change substantially, your body composition has because you have increased your muscle mass and lost body fat.

Also, as we age we tend to lose muscle. This results because our body's functioning capacity reduces but also because our metabolism slows down due to a loss of muscle mass, which results from inactivity. Just as the saying goes: ?use it or lose it?. In fact, research shows us that from the age of 30 to 65 most people have halved their muscle mass and doubled their fat mass and this is often called the ?middle-age spread?. The ?middle-age spread? can easily be prevented or reduced by simply maintaining your muscle mass and therefore your metabolism through weight training.

Thyroid function

The gland that directly affects the metabolism of all body cells is the thyroid gland, which is situated around the trachea in the throat. The thyroid gland produces the throid hormones, thyroxine (T4) and tri-iodothyronine (T3) and these hormones directly increase the metabolism of all body cells. T3 is actually five times more powerful than T4.

The thyroid gland's functioning is affected by many factors. Primarily, meal frequency and nutrient intake.

Nutrition experts recommend we have 5-6 small meals each day spread out every 2-3 hours. By doing so, we tell our body that we have a continual supply of nutrients. If we go without a meal for around 4 hours or more the body's starvation mechanism kicks in and the first thing that occurs is the body reduces it's output of thyroid hormones.

The starvation mechanism is an evolutionary response to a low blood glucose (sugar) level. It helped our ancestors survive famines thousands of years ago. Unfortunately the same thing occurs in our body as well. Whenever our blood glucose drops too low, our output of thyroid hormones decreases, which slows down the metabolism of all body cells, therefore preserving energy and helping us survive the ?famine?.

Also, certain nutrients influence the functioning of the thyroid gland. Kelp (a type of seaweed that is a good source of iodine) and the mineral selenium have been shown to have a direct impact on the functioning of the thyroid gland. When these nutrients are supplemented in the diet they increase the output of thyroid hormones, even in people with normal functioning thyroid glands. Of course, an increase in the output of these hormones boosts the metabolism of all body cells.

Sympathetic tone

Sympathetic tone is the term used to describe the amount of norepinephrine (NE) released from the ends of neurons. Norepinephrine is a neurotransmitter (nerve transmitter) and the more NE is released, the higher the sympathetic tone or metabolic activity of many organs within the body. This means the body's metabolism speeds up.

The people who can eat everything and not put on weight generally have a naturally high sypathetic tone and those people who put on weight just by looking at food tend to have a low sympathetic tone.

The easiest way to increase your sympathetic tone is by using ?thermogenics?. Thermogenesis, as the name suggests, means the production of heat within the body [?thermo?: heat, ?genesis?: the beginning]. Heat is a by-product of energy production, therefore if you burn up more fuel, you generate more heat.

Some examples of thermogenics include certain foods like, coffee or cocoa (caffeine and theobromine- in cocoa) and chilli (capsaicin) and certain herbs (forskolin, evodiamine and ephedra). Green tea also has a very mild thermogenic effect but is mainly used as a ?thermogenic extender?, which means it helps the thermogenics last longer in the body.

Thermogenics have a powerful effect on your metabolism so it is worthwhile ?cycling? their use, which means use them for a period of time, say eight weeks and then stop them for 2-4 weeks. You may also want to use them for two days on and one day off during the 8-week cycle.

So there you have it! Now you've go no more excuses for having a slow metabolism and you have some powerful strategies for boosting your metabolism and easily shedding those unwanted kilos in the lead-up to summer. Plus, there is a simple test to determine your metabolic rate and see if it is necessary to employ any of these strategies (see Ad on this page).

A summary of the strategies is as follows:

oWeight train twice a week.

oHave 5-6 small meals each day

oSupplement your diet with kelp and selenium*

oUse thermogenics occasionally*

So go to it and start turning your body into that fat-burning machine so by the time summer comes around you'll be ready to put on your bathing suit with confidence!

* Before using any nutritional supplement, speak with your health care professional.