In thermodynamic chemistry, the first law state that energy cannot be created nor destroyed but can be transferred from one form of energy to another e.g. from chemical energy to heat energy. It is known that carbohydrates have different relative atomic mass depending on the structures. For example glucose is different from cellulose. In other word monosaccharide are different from polysaccharides and hence the mass. From various experiments done by the experts, low-polysaccharides, high-amino acids diets have adverse effects on the body mass and composition that is independent of the amount of energy taken. This in some ways supports the proposed metabolic advantage of these diets. Therefore weight management is a complicated issue and especially when other factors such as stress that can change the satiety center and intestinal problems that causes poor absorption and assimilation are not put into account. Again such factors can cause hormonal imbalance in the body. In this type of experiments, various factors have to be observed for example final excretion, perspiration and the fattiness of the person under experiment to avoid misleading results.
As indicated in the introduction, weight management is a complicated issue as compared to calories in the body mass. This is because low-polysaccharides diets have been estimative to cause in greater Weight loss than have low-fat diets, irrespective of similar energy intakes between the stated individuals under experiment.  Another issue that emerges is that weight and body mass depend on the bone mass and water component in the fresh that require input of many factors such as the health of the individual under experiment, as compared to calories.
Starting weight and final weight depend on the metabolic factor and conversion from one form to another. For example, if a specific diet were to increase energy expenditure as compared to another diet for the same energy intake, energy balance would be more negative for the former
diet, and weight loss as indicated would be greater. Although the most important factor of energy expenditure with regard to energy balance is total energy expenditure in the body and the final heat produced plus the work that is done using a given amount of energy. 
From the various experiments performed, it can be concluding that a calorie is a calorie irrespective of the minor nutrients available in that diet.  From thermodynamic chemistry, it is clear that the human body or any other living thing cannot create or destroy energy but can only metabolize energy from one form to another. When comparing energy composition between dietary experiments, it should be noted that the units of food energy are utilizable energy and not gross energy. Unfortunate metabolic energy is much more complicated to determine than is
gross energy. This is indicated by At water
factors in calculating metabolically energy.
In addition, it can be admitted that the substitution of one major nutrients for another have a statistically adverse effect on the expenditure half of the energy balance equation. This happens mostly for high-protein diets. However, evidence indicates that the difference in energy expenditure is minute and therefore accounts for less than one-third of the differences in weight loss that have been reported between high protein or low-carbohydrate diets and high carbohydrate or low-fat diets. Therefore, energy use cannot be regulated by nutrient timing and dietary control especially when one is at rest or doing a minor work. To some extent this makes a difference because at last metabolically energy is not the same as the gross energy. It is indicated that the human body is not perfect in assimilation hence thermodynamics may be not as pure as expected. It has been proved that the energy produced from the burning of food in the body is not the same as the energy available to the body from assimilation of that food. This is because, as stated earlier, some of it is lost in the faeces and urine as heat.
From the above summary, it can be concluded that a calorie is a calorie. This is so from a purely thermodynamic chemistry. This is clear because the human body or any other living organism cannot create or destroy energy but can only convert energy from one form to another. After analyzing critically the energy balance between dietary treatments, it is visible that the units of dietary energy are metabolic energy and not gross energy. This is too unfortunate because utilizable energy is much more complicated to determine than gross energy. This is because the Atwater factors used in calculating metabolic energy are not exact. As mentioned earlier, technical error may occur.
Andrea C Buchholz and Dale A Scholar (2002) Is a calorie a calorie? Washington, DC: National
James W Krieger, Harry S (2007) Effects of variation in protein and carbohydrate intake on body mass, Washington, DC: National Academy Press
Thomas CD, Peters JC, Reed GW (1992), Nutrient balance and energy expenditure during ad libido feeding of high-fat and high-carbohydrate diets in humans, Washington, DC: National Academy Press,
Thermodynamic factors (2007), retrieved on 29th September 2007 available at www.ajcn.org
 Meta-analysis, body composition, high-protein diet, low-carbohydrate diet, weight loss
 Although the general factors could be used
to calculate the metabolizable energy of a mixed diet, they were
in error to some degree for almost any particular single food item.
This error results from differences in chemical structure that can
alter the gross energy per unit weight by up to several percent and,
to a slightly larger degree
 Andrea C Buchholz and Dale A Schoeller from first page.
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