By Elena Voropay

If you are like most women, you have probably lost and gained several kilos throughout the years with noticeable changes in your body, both external and internal. While some of these changes may be related to natural processes of living, sicknesses, and aging, a lot of the things may come as a direct result of your weight fluctuations. Seeing a smaller number on the scale may feel great. We have been taught about the good side of weight loss. On the other hand, we are not prepared for shortcomings, frustrations, unrealistic expectations, and lack of knowledge about body's physiology. Have you ever asked yourself – 'What is going on inside of my body as I lose weight?' If you wonder, here is an answer to your question.

There are a few things involved in your metabolism when your weight changes. In a nutshell, if you take in less calories than you burn during the day, week, month or year, you will lose weight. If 'energy in' is made up of the total amount of calories you eat, 'energy out' translates into three factors.

Contrary to popular belief, most of the calories you burn during the day is not when you exercise, but when you rest. Your heart, lungs, digestive system, and, most importantly, the brain, work 24/7 and require constant energy supply. As a result, about 70 percent of your metabolic demands come from “resting energy expenditure” (REE). If you are moderately active, you burn additional 20 percent of calories during “activity energy expenditure” (AEE). Where are the rest 10 percent? Believe it or not, you melt these through simple food digestion and metabolism or “diet induced thermogenesis” (DIT).

Any manipulation of these changes the proportions. If you want to change your body, you will have to change your lifestyle. And that simply means you need to move more, eat less, reduce stress and hopefully sleep better. All together, this will change your metabolism.

Digestive Yo-Yos

You probably heard it many times when a dieter says: “I almost don't eat at all, but my weight is not going down!” First explanation is because the less you eat, the less calories you burn. Additionally, when there are not enough calories available in the body, metabolic rate drops to adjust for deficiencies. Forget strenous exercise – any physical movement is much harder to accomplish if you have no fuel due to an extremely restrictive diet.

There are many other side effects of poor eating habits – nutrient deficiencies, undesirable changes in electrolytes and minerals in the body, bone loss, hormonal disturbances, digestive problems, and impaired immune function. What's more, your brain function may also be effected because the function of its many chemical messengers directly depends on sustained nutrient supply. Expect concurrent episodes of anxiety and depression, insomnia and fatigue, and poor concentration and coordination.

Losing weight from eating less may lower the DIT down to 5 percent – and this is from the smallest piece of the metabolic puzzle.

Loss of Fat and Muscle

When you lose weight, you lose it from everywhere – water, fat and muscle tissue. If body fat just sits on your hips and thighs thriving on your hunger and appetite, lean mass burns off calories constantly, gives strength, energy and desire to move more. While fat burn may be good, muscle and organ waste is the worst thing imaginable.

Essentially, this is done by a complex process of liver work. This largest gland in the body starts releasing the hormone glucagon which assists in burning fat and muscle stores to get the energy. The body senses the nutrient deprivation and adds work for your liver. When there is not enough calories available for immediate energy, especially from carbohydrates, blood sugar levels stay low. As a result, pancreas can't release insulin. But the body needs to keep going maintaining all the metabolic functions. So, it switches to the last resort – breakdown of tissues.

Deriving energy from fat and protein is difficult on all body cells, so you may constantly feel tired and fatigued. Just 50 percent cut in blood glucose levels can lead to dizziness, nausea and eventually loss of consciousness. Over time, tiredness may become your natural condition and you will find no energy or desire to exercise or even engage in daily activities that used to be fun and enjoyable. Researchers estimate that if you eat 500 calories less than you burn during the day, your metabolism switches to breaking down lean muscle and organ tissues as the major resource. As a bonus you didn't ask for, you may melt a lot less calories and fat during the exercise you push yourself through.

Loss of Endurance, Strength and Power

If you want to lose weight, keep it off, and start burning more calories you have to exercise. You know that exercise burns extra calories, melts away the stubborn fat and helps you preserve and maybe even build lean muscles that keep your metabolism sky-high. Even though it comprises only 20 percent of all calories you burn during the day, physical activity helps to maintain and build new muscle tissue – the powerhouse of resting metabolic rate.

If you have a fountain of energy in your body, you can exercise for longer and at higher intensity. This means you are able to burn more calories just through exercise and tilt the 20 percent scale way up! Not only physical activity feels great sending endorphins throughout the circulation to the brain, but it boosts your metabolism, improves digestion, and even makes positive changes in your hormone levels. However, when you lose weight, your fuel tanks may not be up the par to give you all the benefits of exercise.

Besides not being able to maintain the inevitable loss of lean muscle tissues related to aging, you may see a drastic drop in your endurance, strength, power, and, ultimately, additional muscle mass. All of this is reflected on your REE – the calories you burn at rest. So, the last and largest piece of the metabolic puzzle is also cut, let's say by another 10 percent. In the long run, all these reductions add up to a sustained slow metabolism – the famous 'yo-yo-diet' plethora.

Rapid Weight Loss

If you notice your weight is up one day, down the next, you may become confused. Short-term weight loss and gain is not related to how much you've been eating and how much energy you burned during the past day, week, or month. Rather, the ups and downs come from loss or gain of water and digested food. Some days you may find yourself bloated, or your stomach may feel fuller than usual and you feel constipated. All that bulk contributes to your total body weight giving you an unwanted reading on the scales. Keys To Success

The best way to get lean and maintain as much muscle as you can is to diet slowly. Ideally, you should aim to lose no more than ½ kg per week. Any more than that and you are sacrificing muscle.

A successful fat loss program should include:

1. A calorie-restrictive but well-balanced diet with foods from all major food groups

2. Regular cardiovascular activity for at least 30-45 minutes 3-4 times per week.

3. Regular resistance or weight training program at least once or twice a week that includes exercises for all large muscle groups (legs, back, chest).

It all sounds plain and simple, but the key here is consistency. Stay loyal to your program. Take responsibility to commit to your healthy lifestyle - the payoff is well worth the trouble. And remember, it's never too late. If you have tried it before, but failed to continue, look back and see what was the reason. Were you pushing yourself too hard? Did you get discouraged because you didn't see expected results? Maybe you need some patience and persistency in achieving your goals. And what's the rush? You've got a whole life in front of you, so live it, and enjoy every single moment of it.