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2. The origin and maintenance of metabolic allometry in animals

Author

White, Craig R., Marshall, Dustin J., Alton, Lesley A., Arnold, Pieter, Beaman, Julian E., Bywater, Candice L., Condon, Catriona, Crispin, Taryn S., Janetzki, Aidan, Pirtle, Elia, Winwood-Smith, Hugh S., White, Craig R., Marshall, Dustin J., Alton, Lesley A., Arnold, Pieter, Beaman, Julian E., Bywater, Candice L., Condon, Catriona, Crispin, Taryn S., Janetzki, Aidan, Pirtle, Elia, and Winwood-Smith, Hugh S.

Abstract

Organisms vary widely in size, from microbes weighing 0.1 pg to trees weighing thousands of megagrams — a 1021-fold range similar to the difference in mass between an elephant and the Earth. Mass has a pervasive influence on biological processes, but the effect is usually non-proportional; for example, a tenfold increase in mass is typically accompanied by just a four- to sevenfold increase in metabolic rate. Understanding the cause of allometric scaling has been a long-standing problem in biology. Here, we examine the evolution of metabolic allometry in animals by linking microevolutionary processes to macroevolutionary patterns. We show that the genetic correlation between mass and metabolic rate is strong and positive in insects, birds and mammals. We then use these data to simulate the macroevolution of mass and metabolic rate, and show that the interspecific relationship between these traits in animals is consistent with evolution under persistent multivariate selection on mass and metabolic rate over long periods of time.

Published
2019

7. Low-carbohydrate diet induces metabolic depression: a possible mechanism to conserve glycogen.

Author

Winwood-Smith HS, Franklin CE, and White CR

Subjects
Animals, Dietary Carbohydrates administration & dosage, Energy Metabolism drug effects, Female, Male, Physical Exertion drug effects, Diet, Carbohydrate-Restricted methods, Dietary Carbohydrates metabolism, Drosophila melanogaster physiology, Energy Metabolism physiology, Glycogen metabolism, Physical Exertion physiology
Abstract

Long-term studies have found that low-carbohydrate diets are more effective for weight loss than calorie-restricted diets in the short term but equally or only marginally more effective in the long term. Low-carbohydrate diets have been linked to reduced glycogen stores and increased feelings of fatigue. We propose that reduced physical activity in response to lowered glycogen explains the diminishing weight loss advantage of low-carbohydrate compared with low-calorie diets over longer time periods. We explored this possibility by feeding adult Drosophila melanogaster a standard or a low-carbohydrate diet for 9 days and measured changes in metabolic rate, glycogen stores, activity, and body mass. We hypothesized that a low-carbohydrate diet would cause a reduction in glycogen stores, which recover over time, a reduction in physical activity, and an increase in resting metabolic rate. The low-carbohydrate diet reduced glycogen stores, which recovered over time. Activity was unaffected by diet, but metabolic rate was reduced, in the low-carbohydrate group. We conclude that metabolic depression could explain the decreased effectiveness of low-carbohydrate diets over time and recommend further investigation of long-term metabolic effects of dietary interventions and a greater focus on physiological plasticity within the study of human nutrition., (Copyright © 2017 the American Physiological Society.)

Published
2017
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