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Old 11-17-2005, 06:35 AM
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Default Research Question of the Week: A Comprehensive Discussion on Diet Induced Thermogenesis

Bodybuilders are continually searching for methods to increase fat metabolism. The most important variable to consider for this goal is the amount of calories you metabolize.

There are 3 primary avenues for this: Basal Metabolic Rate (BMR), Exercise, and Diet Induced Thermogenesis (DIT).

BMR is the basic energy requirements needed to maintain vital organs such as the liver and kidney, as well as muscles, which can obviously be manipulated and will greatly increase your BMR. Typically, this accounts for 65% of daily oxidative metabolism. A negative energy balance tends to decrease BMR. Therefore, utilizing methods such as carb cycling, calorie cycling, and avoiding starvation diets is vital for maintaining a high BMR.

Exercise can come in the form of resistance training and aerobics. The amount of calories metabolized from this avenue is dependent on the athletes training program, and can vary considerably.

The last avenue by which we metabolize calories is perhaps the least considered one. This is known as diet induced themorgenesis (DIT). DIT is the increase in the amount of the calories metabolized caused by eating foods. Typically, this accounts for 10% of the calories you metabolize. DIT is determined by several variables including: how many calories you eat, exercise, body composition, the type of macronutrients you consume (fat, carbs, or proteins), and also, the type of fats, carbs, and proteins you consume.

Evidence suggests that lean individuals have a higher DIT than obese individuals. It is suggested that obese individuals have a reduced DIT as a consequence of reduced insulin sensitivity and reduced insulin induced sympathetic tone stimulation and thyroid secretion.

A way to acutely improve DIT is through exercise, which incidentally, enhances insulin sensitivity. Therefore, it is commonly advised to train before eating carbohydrates, to enhance insulin sensitivity, and therefore, DIT.

Chronically, methods which enhance insulin sensitivity may further enhance DIT.

Proteins and carbohydrates generally elicit the highest DIT. This may be caused in part by increased insulin secretion. In contrast, little DIT is found from eating fats. However, this is not always the case.

Here is a quote from Venom (2003), Essential Fatty Acids - An In Depth Analysis


The omega-3 has the distinctive ability of enhancing thermogenesis and lipid metabolism (increased usage of fat), thereby reducing body fat deposition. Clarke SD contributes to this, stating, ‘[Omega-3s exert their] effects on lipid metabolism and thermogenesis by up-regulating the transcription of the mitochondrial uncoupling protein-3, and inducing genes encoding proteins involved in fatty acid oxidation (e.g. carnitine palmitoyltransferase and acyl-CoA oxidase) while simultaneously down-regulating the transcription of genes encoding proteins involved in lipid synthesis (e.g. fatty acid synthase) [14].'

The effect of what they are saying is this: food, as well as our own body, contains what is known as ‘potential chemical energy.’ That is, energy held within the bonds of molecules. A good analogy is to think of a boulder placed on a 100 foot hill. By position, when the bolder is on top of the hill, it has the potential to turn into kinetic energy (the energy of movement) if someone were to tip it off the hill so that it began to roll. High-energy bonds within molecules are high-energy because when those bonds are broken, energy is released, which can be used to do work (force x distance=work).

They use the term Lipid Oxidation for a very specific purpose. The organelle in your body known as mitochondria is responsible for extracting energy from lipids (fats), and using it to synthesize or build our energy currency known as ATP (refer to Adam’s tibialis article). Oxidation is referred to because oxygen is required for this process to occur (oxidation refers to an atom accepting electrons from another atom). The entire process is known as cellular respiration, because you need the respiratory system to consume the oxygen needed for the extraction of energy from these food groups, or stored energy deposits such as your own adipose tissue. Carnitine is an essential protein needed for fat breakdown, and thus, when the body encodes for more of it and other vital proteins required for this process, fat breakdown increases. Genes code for proteins. Likewise, by down-regulating certain genes which code for proteins that enhance the formation of fatty molecules, you logically slow down the process. As a result, the above effects are additive to enhanced fat-burning.

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Other fats such as medium Chain Triglycerides should also have a higher DIT response than other fats. For more information on MCT’s, refer to the last research question of the week, Research Question of the Week: How to Optimize Fat Efficiency in the Diet

With all these variables that can potentially manipulate DIT, a summary of the data would be of practical importance to bodybuilders. Therefore, the purpose of this thread was to engage in a comprehensive discussion on DIT. First, mechanisms by which DIT works in the human body need to be understood in order to effectively manipulate it. Second, we need to discuss the influence of obesity, insulin sensitivity, and any other bodily factors that can influence DIT. Third, once these bodily factors have been identified, how can they be positively enhanced to improve DIT. Fourth, what is the effect of the 3 macronutrients on DIT. And finally, are there differences within these macronutrients in producing DIT.
Gabriel "Venom" Wilson, Ph.D. Nutritional Sciences
B.S. (Hons) & M.S. in Kinesiology, CSCS
Vice President, ABCbodybuilding
Co-Editor. of JHR
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