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What is Metabolism? | Metabolic Rate | Metabolic Disorders |
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Looking to lose a few pounds? Confused about your body’s energy utilization? Curious about how your body takes in food? Maybe you should try learning more about metabolism. Understanding the way food is ingested and utilized in the body to release energy will give you a better idea as to how to tailor your diet and exercise according to your needs.

  1. MetabolismWhat is Metabolism?
  2. What is Metabolic Rate?
  3. Thermic Effect of Food (TEF)
  4. Factors affecting Metabolism
  5. Importance of Nutrition
  6. Metabolic States
  7. Metabolic Disorders
  8. Symptoms of Metabolic Disorders
  9. Treatment of Metabolic Disorders


What is Metabolism?

Metabolism essentially includes all the chemical reactions being carried out in the body to maintain life. It involves the usage of hormones and enzymes to convert your food in to energy, and also to use the energy to carry out all life sustaining processes.

Metabolism can be classified into:

  • Anabolism, which is the utilization of energy for the synthesis of compounds needed by the cell and,
  • Catabolism, which is the process of breaking down of substances to release energy.

Metabolism is essentially the amalgamation of metabolic rate, the thermic effect of food and physical activity. We start off with defining Metabolic Rate.

What is Metabolic Rate?

Metabolic rate is basically the amount of energy released in a given time. Usually it is calculated as Basal Metabolic rate (BMR) or Resting Metabolic Rate (RMR). BMR or RMR is the amount of energy utilized when our body is in complete rest, to perform the necessary functions of maintenance of the heart rate, breathing, and state of consciousness. It is calculated by measuring the heat given off per unit time and is expressed as the number of calories given off per kilogram of body weight. You can use it to analyze how active your metabolic system is.

Thermic Effect of Food (TEF)

The thermic effect of food is the amount of energy, additional to the resting metabolic rate, required to digest, absorb and store food in the body. Its amount depends on the various nutrients taken in the diet. For example, Fats are easily digested and so have a low thermic effect. On the contrary, Proteins are harder to process and thus have a high thermic effect.

Factors affecting Metabolism

Our body’s metabolism is lowest while we are sleeping. The basal metabolic rate of each individual varies based on several factors as mentioned below:

  • Body mass: A person with a greater body weight will have a higher resting metabolic rate as body works more to meet the requirements of the extra weight.
  • Age: metabolism declines naturally with age at a rate of 2-3% per decade because of the declining lean muscle mass
  • Heredity
  • Body composition: Muscle burns more energy than fat. One kilogram of muscle expends 3-5 times the calories that one kilogram of fat burns.
  • Gender: Men have a higher basal metabolic rate as compared to women which can be explained by their body mass and composition
  • Stress: Stress increases the body’s metabolic rate because of the release of stress hormones like epinephrine and norepinephrine. Furthermore, these stress hormones lead to an increase in respiratory rate and heart rate which consumes more energy.
  • Sleep: Going to bed early helps speed up metabolism. Sleep deprivation results in body stress and increases visceral fat which slows metabolism.
  • Foods that enhance metabolism: There are certain food substances that help speed up the process of metabolism. Grapefruit helps speed metabolism by reducing insulin levels in the blood. Hot peppers contain a substance called capsaicin which boosts metabolism hours after you eat. Lean proteins in chicken and turkey consume a lot of energy when our body breaks them down. Fish oil in salmon and tuna helps lower leptin levels which is a hormone linked with slower metabolism and weight gain. Green tea accelerates your heart rate and contains a chemical call EGCG which boost metabolism. Calcium and Vitamin C also have a role in speeding up the body metabolism.
  • Dietary habits: The idea of restricting food intake to help lose weight is a misconception. This is because our body responds to starvation by reducing the metabolic rate. Moreover once your body starts burning muscle weight, it gives the body fat an advantage to further decrease metabolic rate. The ideal way to maintain a healthy metabolism is to eat multiple small spaced out meals during the day that keep your body full. Breakfast is the most essential meal of the day as it revs up the metabolism and keeps the energy going through the day.
  • Hydration status: Body’s chemical reactions including metabolism depend on water. Dehydration results in burning at least 2% less calories than a well hydrated individual. Drinking 8-12 glasses of water is important to maintain a healthy metabolism. Moreover drinking cold water further enhances the body’s metabolic rate as you burn calories to heat the water to body temperature.
  • Physical Activity: Physical activity is perhaps the only component that you can use easily to manipulate metabolism. The process is very simple. The more physically active you become, the more your metabolism increases. Even moving your hands or legs randomly while sitting can burn up to 600 calories in a day. In the modern age of jobs that involve sitting endlessly staring at a computer screen and food delivery services that record your address for further ease, it is quite a challenge to find the time or energy to get up and exercise. But then again if you utilize less than half of the food you eat, you know where the rest of it is going to end up. Hence, in order to maintain a healthy figure and weight, you must burn as many calories as you take in. Remember, back-splitting exercises and intensely strenuous jogging is not a must. You can burn the same amount of calories jogging for half an hour as you could while taking an hour long walk.

Importance of Nutrition

A balanced diet is one that contains all the nutrients in adequate amounts. You already know the six essential nutrients; Carbohydrates, Proteins, Fats, Vitamins, Minerals and Water. What you might not know is that some of these are further classified into essential, semi-essential and non-essential.

  • Essential nutrients are those which are not made by the body, and so you need to take them in your diet regularly. If you fail to do so, a lot can go wrong and development and growth can be gravely affected.
  • Semi-essential nutrients are those which the body makes in small amount. In growing children, lactating and pregnant women, these nutrients are not enough and so they should be included in the diet.
  • Non-essential nutrients are those which the body makes in adequate quantity.

Thus, you can understand how closely linked nutrition and metabolism are and how essential it is to maintain a healthy intake of food.

Metabolic States

To further understand how your body carries out the different processes of metabolism, you can learn about metabolic states.

  • Dynamic Catabolic-Anabolic State: During which organic molecules are constantly being broken down and synthesized.
  • Absorptive Stage: Which takes place while eating food when food has been digested and nutrients are being absorbed in the intestines. Anabolism is taking place more than catabolism and the major source of energy is Glucose.
  • Post-absorptive Stage: When the Gastro-intestinal tract is empty and energy is released by breaking down nutrients that have been stored in the liver. The main goal during this stage is to maintain blood sugar and prevent it from dropping in the period between your meals. Hence it signifies the start of catabolism.

Metabolic Disorders

Metabolic disorders are those which interfere with metabolic pathways and prevent the normal breakdown and absorption of food. Most people suffering from metabolic disorders have an abnormal gene which results in the deficiency or malformation of a hormone or enzyme. Since the particular hormone or enzyme cannot function properly, metabolism is gravely affected in various ways. It may be that the defective or missing enzyme was responsible for detoxifying reactions. This would mean the buildup of toxic materials that cause harm to the body. The defective enzyme could also be essential for synthesizing a substance that is important for the body. This in turn would lead to a deficiency disease.

Examples of some common metabolic disorders are given below:

  • Lysosomal storage disorders, such as Krabbe disease and Tay Sacchs disease, involve deficiency of enzymes within lysosomes. Lysosomes are enzyme containing sacs in the cell that are responsible for breaking down all the food a cell ingests.
  • Galactosemia which is the impaired breakdown of Glycogen in newborns, leading to diarrhea, vomiting and jaundice.
  • Phenylketonuria which results in increased levels of phenylalanine (an amino acid) in the blood due to deficiency of an enzyme. It can cause mental retardation if not treated.
  • Maple Syrup Urine disease, another enzyme deficiency disease which causes buildup of amino acids and nerve damage.
  • Mitochondrial disorders are due to some problems in the mitochondrial metabolism, resulting in muscle damage.
  • Peroxisomal Disorders which lead to accumulation of toxic products inside the body. Peroxisomes are small sac like bodies in the cell which are responsible for detoxification.
  • Metal metabolism disorders, like Wilson disease and Hemochromatosis, are inherited metabolic disorders which result in lethal accumulation of metal in the body.
  • Glycogen storage diseases like Diabetes lead to problems with storage of sugar, causing high blood sugar level, muscular pain and weakness.

Symptoms of Metabolic Disorders

Since there are a number of different metabolic disorders, symptoms may vary widely. The onset of symptoms may also vary, some becoming apparent at birth, whilst others appearing later or due to aggravation by diet, medication or dehydration. Most metabolic disorders that are present at birth are detected and diagnosed by routine screening. Others remain undiagnosed till symptoms appear.

These are some of the symptoms that appear due to a metabolic disorder:

  • Poor appetite
  • Abdominal pain
  • Lethargy
  • Vomiting
  • Weight loss
  • Jaundice
  • Failure to grow
  • Seizures
  • Comma
  • Foul smelling bodily fluids or breath

Treatment of Metabolic Disorders

Since most metabolic disorders are due to defective genes, the current technology is not advanced enough to provide a certain cure. Instead treatments aim to work with the defect intact by making it easier for the patient to metabolize food. These include:

  • Taking enzyme supplements in order to replace a defective or missing enzyme, so that normal synthesis or breakdown of materials can occur. As is obvious, the patient will have to take the supplements his whole life so as to have normal metabolism.
  • Treating the blood with detoxifying chemicals in place of the defective or missing enzyme that is normally responsible for detoxification. Again, in order to prevent accumulation of the lethal substance, treatment will have to be continued throughout the life time.
  • Diets that eliminate certain nutrients, the enzymes of which are either missing or defective. In this way extra supplements or enzymes need not be taken.

Metabolic disorders should not be taken lightly. Usually complaints of abdominal pain, lethargy and poor appetite go unnoticed, but it is essential to seek immediate medical care. Often children and adults suffering from metabolic disorders seek help too late, leading to the need of hospitalization and sometimes even life support. Hence it is important to take special care of your body’s metabolism.