Isocaloric diet

The preparation time for a PER is extensive and involves several days for acquisition of rats and their acclimation before a feeding trial begins. Preparation of a consistent and uniform diet is not trivial. Adequate diet for each treatment for the course of the study should be prepared shortly in advance of the study. Testing of the diet involves chemical analysis for protein (i.e., Kjeldahl N takes several hours) and accurate determination of other diet constituents (e.g., ash, crude lipid, and dietary fiber) so that isocaloric diets can be formulated between treatment groups. These determinations take >1 day to complete. It is recommended that multiple samples from each diet be obtained for proximate analysis of diet before it is fed to ensure that each diet has the proper nitrogen content (and this is same between diet treatments) and that all diets are isocaloric. 

Studies on starvation, however, are compatible with a major effect of changing the proportion of the macromolecular constituents of isocaloric diets. This reconciliation of seemingly contradictory results offers an opportunity to stress the complex effects of several dietary factors and the possibility for interactions among them. 

In addition, we know that changing a customary diet to one high in protein and low in carbohydrate in some people, increases the rates of metabolism of drugs such as antipyrine and theophylline, and shifting to an isocaloric diet of low protein-high carbohydrate slows the rates of metabolism of these drugs. However, numerous studies emphasize the considerable individual variability to changes in human diets some people exhibit dramatic effects others exhibit little or no response. 

When included as part of an isocaloric diet or a weight-loss intervention, the current literature does not show a consistent beneficial effect of soy protein and/or isoflavones on glycemic control. This is largely due to the small number of studies. Additional research is required to increase our understanding of the effects of soy protein on measures of glycemic control. 

All studies were conducted in the morning following an overnight fast. Medication known to effect the level of serum uric acid or urinary uric acid excretion was withdrawn at least 4 days prior to the studies. All subjects were maintained on a purine-free, low protein, isocaloric diet for at least 3 days prior to and throughout the studies. 

Ernest, I., Hallgren, B., and Svanborg, A., 1962, Short-term study of effect of different isocaloric diets in diabetes. Metabolism 11 912. 

All three patients were hospitalized on the Clinical Research Unit of Duke University Medical Center and received isocaloric diets which, as specified later, contained a normal amount of dietary purines, were essentially free of purines or contained the amount of adenine (10 mg/Kg/day in four divided doses) roughly equivalent to the normal daily intake. All three patients received allopurinol (150-300 mg/day) orally throughout the entire period of study. 

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