Introduction
In mid 16th century, a Latin verb called “intermittere” was formed which was later ceased as “intermittent”. So intermittent mean occurring at irregular intervals or not continuous, etc. Intermittent fasting and caloric restriction extends the lifespan and behave as resistance to age-related diseases and also increases the health of overweighed humans. It also shows several other health benefits which include insulin sensitivity, stress resistance, induced morbidity. Caloric restriction and intermittent fasting affect energy and oxygen radical metabolism, and cellular stress response system in ways that protect neurons against genetic and environmental factors to which they would fail to resist during aging. Metabolism refers to the entire range of process of all the biochemical reactions that happens within a living organism. All the calories of food and beverages that is taken inside the body combine with oxygen to release the energy which the body needs to function. So according to the difference in the fasting period, the effects in the homo sapiens are discussed in the cases below that help us to know what all changes occur during intermittent fasting
CASE 1
Alternate day fasting on non-obese subjects: effects on body weight, body composition, and energy metabolism.
Design : nonobese subjects (8 men, 8 women) were kept in dietary restriction every other day for 22 days, body weight, body composition, resting metabolic rate, respiratory quotient, temperature, fasting serum glucose, free fatty acids and insulin were assessed at the baseline and after 21 days (12 hr fast) and 22days (36 hr fast) of alternate day fasting. Visual analog scales were used to asses hunger weekly.
Result: subjects have lost their initial fat mass and initial body weight. It was also found that significant increase in case of the feelings of hunger and a significant decrease in the feeling of fullness. Repeated analysis over time showed no significant changes on the subjects ‘ perception of hunger, thirst, feelings of satisfaction, desire to eat, though feelings of fullness slightly increased over-time. Fat oxidation increased and carbohydrate oxidation decreased over the time. During fasting, glucose level was not significantly changed and insulin level was lowered in both men and women, free fatty acids concentration were higher in both men and women on day 22.
Conclusion: intermittent fasting was feasible on the subjects, and fat and oxidation increased. Although hunger on fasting days did not reduce. It was also found that adding a small meal on the day of fasting will be more efficient to get better results on dietary restrictions.
CASE 2
Prolonged fasting changes nutrient oxidation and glucose tolerance after a normal mixed meal.
The aim of this study was to design an experimental model of fasting, followed by refeeding, to investigate individual differences in nutrient partitioning.
Design: 8 non-obese men were fed with the normal meal, on two occasions, after an overnight (13 hrs) fast and after a prolonged (72hrs)fast. During the entire period, the subjects were resident in a whole room that is indirect calorimeter, and blood samples were drawn and periodically determined.
Result: since no food was consumed over the 12 hrs after either meal, negative energy balance was observed after the overnight and prolonged fast. Consumption of meal after typical overnight fast results in a rapid transition from predominantly fat oxidation to carbohydrate oxidation. Postprandial hormonal changes elevated glucagon, cortisol, and norepinephrine, after 72 hrs of fasting, decreased postprandially in contrast to this 13hrs of fasting showed little change in the level of cortisol and norepinephrine. Postprandial carbohydrate oxidation was significantly reduced after the 72 hrs vs.13 hrs, whereas fat oxidation was significantly increased. Engrossingly carbohydrate balance was positive after the prolonged fast but negative after the overnight fast whereas fat balance was negative under both conditions. It appears that the extent to which ingested carbohydrate promotes its own oxidation is partly dependent on the individual energy status. After 72 hrs of fast glucose and insulin excursions in response to the mixed meal were significantly greater compared with 13hrs fast.
Conclusion: Prolonged fasting resulted in significant decrease in carbohydrate oxidation whereas an increase in fat oxidation, after a normal fixed meal, as it was associated with significant decrease in the glucose tolerance. Its cause the circulating free fatty acids were greatly evaluated at all time, after the prolonged fast, these maybe mediating changes in postprandial metabolism. It would be interesting to determine the substrate and hormone response to refeeding the mixed meal in other population including obese individuals and diabetic individuals.
CASE 3
Effects of intermittent fasting and refeeding on insulin action in Healthy Men.
Resistance towards insulin is currently the major health problem. This may be because of markedly decrease in daily physical activity and combined with constant food abundance. This lifestyle collides with the genome, which was most likely selected in the late Palaeolithic era (50,000-10,000BC) by criteria and this favoured survival in an environment characterized by fluctuations between periods of feast and famine. And the theory of thrifty genes states that these fluctuations are required for optimal metabolic function.
Design: Eight healthy young Caucasian men were subjected to intermittent fasting. Subjects were examined on two occasions; before and after 14 days of fasting every second day of 20 hrs, giving seven fasting periods. Each period started at 2200and ended at 1800 the following day. During the fasting period, the subjects were allowed to drink water and maintain their habitual activities. Micro dialysis was performed for each of the subjects. Plasma glucose concentration was also maintained at pre-experimental level by frequent analysis of blood samples with ensuring adjustments in glucose infusion rate. Blood flow, muscle biopsies, total protein concentration, blood sample, and analysis were done and the result was discussed also in the ANOVA table.
Result: the body weight was maintained and also the body fat did not change even after the intervention of fasting. Since the habitual activities were done regularly thus the average heart rate was normal during daytime as on the fasting period as well as during the non-fasting period. during the fasting process compared to normal daytime showed that the glucose infusion rate was significantly increased on the last 30 mins of the fasting period. The absolute interstitial glycerol concentration and the adipose tissue blood flow rate either of them showed no effect due to intermittent fasting. This indicated that insulin had enhanced the inhibitory effect on lipolysis due to intermittent fasting. After 20 hrs fasting the plasma glucose concentration was lower as compared to short fasting period of 8 hrs. As of result during 8 hrs fasting the β – hydroxybutyrate, free fatty acid, and glycerol concentration were all similar before and after fasting period, and all decreased with insulin infusion whereas after 20 hrs of fasting all the above concentration were increased but increase in β- hydroxybutyrate did not attain any statistical significance.
Conclusion: it was found that fasting every second day increased the insulin sensitivity approximately sevenfold and decreased the incidences of diabetes. With the present fasting protocol and maintenance of habitual physical activity detected a decrease in IMTG content in skeletal muscles. Therefore fasting for 20 hrs while maintaining normal physical activity caused a temporary negative energy balance larger than normally experienced on the daily basis, it also indicated a decrease in the plasma glucose concentration. Since the energy stored in the adipose tissue was not measured during the action, therefore we cannot determine whether the change in adipokine release is merely a secondary response to intermittent fasting or whether the adipose tissue is an active recognizer of energy oscillations.
CASE 4
Effect of sodium in rehydration beverage when consumed as a fluid or meal.
Evidence from few studies that have examined post-exercise rehydration supports the addition of electrolytes, particular sodium as a promotion to body water restoration. According to Costill and Sparks (8) observation, it was also seen that carbohydrate-electrolyte beverage have greater plasma recovery than in those consuming water after dehydration. Thus body water restoration can be accelerated when beverages consumed with a higher level of sodium or carbohydrate-electrolyte beverage. It also shows that the consumption of these beverages will provide better rehydration result after long-term fasting.
Design: thirty subjects underwent a combination of thermal and exercised induced dehydration and then 2 hrs rehydration period with one of four different beverages in a randomized crossover. The blood sample, heart rate, rectal temperature, total urine volume, specific gravity and sodium potassium concentration were all determined. After rehydration subjects underwent a transition period to allow the body fluid to stabilize.
Result: there were no significant differences in body weight before and after rehydration or in percent change in body weight after dehydration with respect to trials. No gastrointestinal stress was recorded during rehydration period. The urine volume measured at the end of the rehydration period was significantly greater but no significant difference in the urine specific gravity in the trials.
Conclusion: the addition of sodium to rehydration beverage significantly increases fluid retention in extracellular space, leading to a greater plasma volume observation than in observed after ingestion of water and dilute electrolyte solutions.
Conclusion
According to the studies done in order to find the effect that occurs due to intermittent fasting showed that when we add a small meal during the fasting period can give more efficient result during the prolonged fasting period, the fasting period also showed significant effect in the increased insulin sensitivity which lead to decreased in the diabetic level. The fasting can also be stimulated by consumption of the sodium electrolyte beverages to avoid loss in the body weight as well as the body water concentration, this can be done instead of small meal addition. Hence the cases discussed above showed that the body metabolism can be improved with a small as well as prolonged fasting.