Starvation physiology: reviewing the different strategies animals use to survive a common challenge.
01 May 2010-Comparative Biochemistry and Physiology A-molecular & Integrative Physiology (Comp Biochem Physiol A Mol Integr Physiol)-Vol. 156, Iss: 1, pp 1-18
TL;DR: The various physiological strategies that allow different animals to survive starvation are characterized and areas in which investigations of starvation can be improved are identified to facilitate meaningful investigations into the physiology of starvation in animals.
Abstract: All animals face the possibility of limitations in food resources that could ultimately lead to starvation-induced mortality. The primary goal of this review is to characterize the various physiological strategies that allow different animals to survive starvation. The ancillary goals of this work are to identify areas in which investigations of starvation can be improved and to discuss recent advances and emerging directions in starvation research. The ubiquity of food limitation among animals, inconsistent terminology associated with starvation and fasting, and rationale for scientific investigations into starvation are discussed. Similarities and differences with regard to carbohydrate, lipid, and protein metabolism during starvation are also examined in a comparative context. Examples from the literature are used to underscore areas in which reporting and statistical practices, particularly those involved with starvation-induced changes in body composition and starvation-induced hypometabolism can be improved. The review concludes by highlighting several recent advances and promising research directions in starvation physiology. Because the hundreds of studies reviewed here vary so widely in their experimental designs and treatments, formal comparisons of starvation responses among studies and taxa are generally precluded; nevertheless, it is my aim to provide a starting point from which we may develop novel approaches, tools, and hypotheses to facilitate meaningful investigations into the physiology of starvation in animals.
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TL;DR: Exogenous ketone drinks are concluded to be a practical, efficacious way to achieve ketosis and had similar effects on blood electrolytes, which remained normal.
Abstract: Background and aims: Currently there is considerable interest in ketone metabolism owing to recently reported benefits of ketosis for human health. Traditionally, ketosis has been achieved by following a high-fat, low-carbohydrate ‘ketogenic’ diet, but adherence to such diets can be difficult. An alternative way to increase blood D-β-hydroxybutyrate (D-βHB) concentrations is ketone drinks, but the metabolic effects of exogenous ketones are relatively unknown. Here, healthy human volunteers took part in three randomized metabolic studies of drinks containing a ketone ester (KE); (R)-3-hydroxybutyl-(R)-1,3-hydroxybutyrate, or ketone salts (KS); sodium plus potassium βHB. Methods and Results: In the first study, 15 participants consumed KE or KS drinks that delivered ~12 g or ~24 g of βHB. Both drinks elevated blood D-βHB concentrations (D-βHB Cmax: KE 2.8 mM, KS 1.0 mM, P < 0.001), which returned to baseline within 3-4 h. KS drinks were found to contain 50% of the L-βHB isoform, which remained elevated in blood for over 8 h, but was not detectable after 24 h. Urinary excretion of both D-βHB and L-βHB was < 1.5 % of the total βHB ingested and was in proportion to the blood AUC. D-βHB, but not L-βHB, was slowly converted to breath acetone. The KE drink decreased blood pH by 0.10 and the KS drink increased urinary pH from 5.7 to 8.5. In the second study, the effect of a meal before a KE drink on blood D-βHB concentrations was determined in 16 participants. Food lowered blood D-βHB Cmax by 33% (Fed 2.2 mM, Fasted 3.3 mM, P < 0.001), but did not alter acetoacetate or breath acetone concentrations. All ketone drinks lowered blood glucose, free fatty acid and triglyceride concentrations, and had similar effects on blood electrolytes, which remained normal. In the final study, participants were given KE over 9 h as three drinks (n = 12) or a continuous nasogastric infusion (n = 4) to maintain blood D-βHB concentrations greater than 1 mM. Both drinks and infusions gave identical D-βHB AUC of 1.3-1.4 moles.min. Conclusion: We conclude that exogenous ketone drinks are a practical, efficacious way to achieve ketosis.
230 citations
Cites background from "Starvation physiology: reviewing th..."
...Human’s ability to produce and oxidize ketone bodies arguably evolved to enhance survival during starvation by providing an energy source for the brain and slowing the breakdown of carbohydrate and protein stores (Owen et al., 1967; Sato et al., 1995; Marshall, 2010)....
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TL;DR: The physiological basis of ketogenic diets and the rationale for their use in obesity are discussed, discussing the strengths and the weaknesses of these diets together with cautions that should be used in obese patients.
Abstract: Obesity is reaching epidemic proportions and is a strong risk factor for a number of cardiovascular and metabolic disorders such as hypertension, type 2 diabetes, dyslipidemia, atherosclerosis, and also certain types of cancers. Despite the constant recommendations of health care organizations regarding the importance of weight control, this goal often fails. Genetic predisposition in combination with inactive lifestyles and high caloric intake leads to excessive weight gain. Even though there may be agreement about the concept that lifestyle changes affecting dietary habits and physical activity are essential to promote weight loss and weight control, the ideal amount and type of exercise and also the ideal diet are still under debate. For many years, nutritional intervention studies have been focused on reducing dietary fat with little positive results over the long-term. One of the most studied strategies in the recent years for weight loss is the ketogenic diet. Many studies have shown that this kind of nutritional approach has a solid physiological and biochemical basis and is able to induce effective weight loss along with improvement in several cardiovascular risk parameters. This review discusses the physiological basis of ketogenic diets and the rationale for their use in obesity, discussing the strengths and the weaknesses of these diets together with cautions that should be used in obese patients.
227 citations
Cites background from "Starvation physiology: reviewing th..."
...Ketone bodies are then used by tissues as a source of energy [25,27,29,30] through a pathway that...
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TL;DR: The aim of this review is to provide a summary of current knowledge of the effects of ketogenic diet (KD) on food control in an effort to unify the apparently contradictory data into a coherent picture.
Abstract: Though the hunger-reduction phenomenon reported during ketogenic diets is well-known, the underlying molecular and cellular mechanisms remain uncertain. Ketosis has been demonstrated to exert an anorexigenic effect via cholecystokinin (CCK) release while reducing orexigenic signals e.g., via ghrelin. However, ketone bodies (KB) seem to be able to increase food intake through AMP-activated protein kinase (AMPK) phosphorylation, gamma-aminobutyric acid (GABA) and the release and production of adiponectin. The aim of this review is to provide a summary of our current knowledge of the effects of ketogenic diet (KD) on food control in an effort to unify the apparently contradictory data into a coherent picture.
176 citations
Cites background from "Starvation physiology: reviewing th..."
...…liver, KBs are used by tissues as a source www.frontiersin.org February 2015 | Volume 6 | Article 27 | 3 of energy (Fukao et al., 2004; Veech, 2004; McCue, 2010): initially BHB is converted back to AcAc that is subsequently transformed into Acetoacetyl-CoA that undergoes a reaction producing two…...
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...These periods of fasting are themselves ketogenic (McCue, 2010) during which the concentrations of insulin and glucose decrease while that of glucagon increases in the attempt to maintain normal blood glucose levels....
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TL;DR: The insurance hypothesis as discussed by the authors is rooted in adaptive evolutionary thinking: the function of storing fat is to provide a buffer against shortfall in the food supply, and individuals should store more fat when they receive cues that access to food is uncertain.
Abstract: Integrative explanations of why obesity is more prevalent in some sectors of the human population than others are lacking. Here, we outline and evaluate one candidate explanation, the insurance hypothesis (IH). The IH is rooted in adaptive evolutionary thinking: The function of storing fat is to provide a buffer against shortfall in the food supply. Thus, individuals should store more fat when they receive cues that access to food is uncertain. Applied to humans, this implies that an important proximate driver of obesity should be food insecurity rather than food abundance per se. We integrate several distinct lines of theory and evidence that bear on this hypothesis. We present a theoretical model that shows it is optimal to store more fat when food access is uncertain, and we review the experimental literature from non-human animals showing that fat reserves increase when access to food is restricted. We provide a meta-analysis of 125 epidemiological studies of the association between perceived food insecurity and high body weight in humans. There is a robust positive association, but it is restricted to adult women in high-income countries. We explore why this could be in light of the IH and our theoretical model. We conclude that although the IH alone cannot explain the distribution of obesity in the human population, it may represent a very important component of a pluralistic explanation. We also discuss insights it may offer into the developmental origins of obesity, dieting-induced weight gain, and anorexia nervosa.
157 citations
TL;DR: In this article, a review of the utility of ketogenic diets in a variety of metabolic diseases such as obesity, metabolic syndrome, and diabetes is presented, and some common mechanisms that could explain the effects of KFD are discussed.
Abstract: An increasing number of data demonstrate the utility of ketogenic diets in a variety of metabolic diseases as obesity, metabolic syndrome, and diabetes. In regard to neurological disorders, ketogenic diet is recognized as an effective treatment for pharmacoresistant epilepsy but emerging data suggests that ketogenic diet could be also useful in amyotrophic lateral sclerosis, Alzheimer, Parkinson's disease, and some mitochondriopathies. Although these diseases have different pathogenesis and features, there are some common mechanisms that could explain the effects of ketogenic diets. These mechanisms are to provide an efficient source of energy for the treatment of certain types of neurodegenerative diseases characterized by focal brain hypometabolism; to decrease the oxidative damage associated with various kinds of metabolic stress; to increase the mitochondrial biogenesis pathways; and to take advantage of the capacity of ketones to bypass the defect in complex I activity implicated in some neurological diseases. These mechanisms will be discussed in this review.
156 citations
Cites background from "Starvation physiology: reviewing th..."
...KBs are used by tissues as a source of energy [19, 21, 23] through a pathway that firstly converts 3HB back to AcAc which is then transformed into acetoacetyl-CoA....
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...The periods of fasting or undernutrition are themselves ketogenic [23] during which the concentrations of insulin and glucose decrease while those of glucagon increase with the attempt to maintain normal blood glucose levels....
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References
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Book•
01 Jan 1966
TL;DR: Textbook of medical physiology , Textbook ofmedical physiology , کتابخانه دیجیتال جندی شاپور اهواز
Abstract: Textbook of medical physiology , Textbook of medical physiology , کتابخانه دیجیتال جندی شاپور اهواز
10,145 citations
TL;DR: Textbook of medical physiology, Textbook of Medical Physiology, this paper, textbook of medicine, textbooks of medical science, text book of medical literature, textbook medical physiology.
9,914 citations
TL;DR: A method of correcting for the phylogeny has been proposed, which specifies a set of contrasts among species, contrasts that are statistically independent and can be used in regression or correlation studies.
Abstract: Recent years have seen a growth in numerical studies using the comparative method. The method usually involves a comparison of two phenotypes across a range of species or higher taxa, or a comparison of one phenotype with an environmental variable. Objectives of such studies vary, and include assessing whether one variable is correlated with another and assessing whether the regression of one variable on another differs significantly from some expected value. Notable recent studies using statistical methods of this type include Pilbeam and Gould's (1974) regressions of tooth area on several size measurements in mammals; Sherman's (1979) test of the relation between insect chromosome numbers and social behavior; Damuth's (1981) investigation of population density and body size in mammals; Martin's (1981) regression of brain weight in mammals on body weight; Givnish's (1982) examination of traits associated with dioecy across the families of angiosperms; and Armstrong's (1983) regressions of brain weight on body weight and basal metabolism rate in mammals. My intention is to point out a serious statistical problem with this approach, a problem that affects all of these studies. It arises from the fact that species are part of a hierarchically structured phylogeny, and thus cannot be regarded for statistical purposes as if drawn independently from the same distribution. This problem has been noticed before, and previous suggestions of ways of coping with it are briefly discussed. The nonindependence can be circumvented in principle if adequate information on the phylogeny is available. The information needed to do so and the limitations on its use will be discussed. The problem will be discussed and illustrated with reference to continuous variables, but the same statistical issues arise when one or both of the variables are discrete, in which case the statistical methods involve contingency tables rather than regressions and correlations.
8,833 citations
"Starvation physiology: reviewing th..." refers background in this paper
...Relative rates of starvation-induced mb loss seem to follow taxonomic lines, but this possibility has not been formally explored using phylogenetically informed comparisons (sensu Felsenstein, 1985)....
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Book•
01 Sep 1993
TL;DR: The fourth edition of Modern Nutrition in Health and Disease follows the organization established in previous volumes, i.e., "Normal Nutrition," "Nutrition in Disease," and "Nut Nutrition in Periods of Physiologic Stress" Each of the 43 chapters is, in essence, a review of a given topic, with primary emphasis on nutritional principles rather than dietetics as mentioned in this paper.
Abstract: The fourth edition of Modern Nutrition in Health and Disease follows the organization established in previous volumes, ie, "Normal Nutrition," "Nutrition in Disease," and "Nutrition in Periods of Physiologic Stress" Each of the 43 chapters is, in essence, a review of a given topic, with primary emphasis on nutritional principles rather than dietetics Three new chapters have been added, two under "Normal Nutrition" and one under "Nutrition in Disease" These are (1) "Naturally Occurring Toxic Foods" by Mickelsen and Yang; (2) "Evaluation of Nutrition in Population Groups" by Pearson; and (3) "Nutrition in Brain Function" by Coursin All are timely, well-written additions to the book The rest of the volume has been revised extensively, and 12 new authors are listed In spite of the expansion in content, the fourth edition contains 20 fewer pages than the previous one, but this was accomplished by increasing the size of the page by
2,968 citations
01 Jan 1968
TL;DR: The concept of nutrition as a clinical subject has reached maturity and is well presented in an excellent book edited by two prominent nutritionists, Drs.
Abstract: MODERN NUTRITION IN HEALTH AND DISEASE , MODERN NUTRITION IN HEALTH AND DISEASE , کتابخانه مرکزی دانشگاه علوم پزشکی ایران
2,720 citations