John Speakman

Chinese Academy of Sciences | CAS · Shenzhen Institutes of Advanced Technology

Human obesity has a large genetic component, yet has many serious negative consequences. How this state of affairs has evolved has generated wide debate. The thrifty gene hypothesis was the first attempt to explain obesity as a consequence of adaptive responses to an ancient environment that in modern society become disadvantageous. The idea is tha...

The impacts of different macronutrients on body weight regulation remain unresolved, with different studies suggesting increased dietary fat, increased carbohydrates (particularly sugars), or reduced protein may all stimulate overconsumption and drive obesity. We exposed C57BL/6 mice to 29 different diets varying from 8.3% to 80% fat, 10% to 80% ca...

The disposable soma hypothesis explanation of the effects of caloric restriction (CR) on lifespan fails to explain why CR generates negative impacts alongside the positive effects and does not work in all species. I propose here a novel idea called the clean cupboards hypothesis which overcomes these problems.

The protein leverage hypothesis predicts that low dietary protein should increase energy intake and cause adiposity. We designed 10 diets varying from 1% to 20% protein combined with either 60% or 20% fat, contrasting the expectation that very low protein did not cause increased food intake. Although these mice had activated hunger signaling, they...

1. The role of energy in ecological processes has hitherto been considered primarily from the standpoint that energy supply is limited. That is, traditional resource-based ecological and evolutionary theories and the recent ‘metabolic theory of ecology’ (MTE) all assume that energetic constraints operate on the supply side of the energy balance equ...

Nutritional epidemiology aims to link dietary exposures to chronic disease, but the instruments for evaluating dietary intake are inaccurate. One way to identify unreliable data and the sources of errors is to compare estimated intakes with the total energy expenditure (TEE). In this study, we used the International Atomic Energy Agency Doubly Labe...

Scope The study assesses the metabolic impact of dietary whey proteins across generations. Method and results Virgin females are fed 20% energy whey proteins with 70% energy carbohydrates, which reduces body weight gain and visceral adipose compared to controls fed dietary casein. In contrast, the males are unresponsive. The effect is accentuated...

Increasing evidence suggests bats are the ancestral hosts of the majority of coronaviruses. In general, coronaviruses primarily target the gastrointestinal system, while some strains, especially Betacoronaviruses with the most relevant representatives SARS-CoV, MERS-CoV, and SARS-CoV-2, also cause severe respiratory disease in humans and other mamm...

The disposable soma theory (DST) posits that organisms age and die because of a direct trade-off in resource allocation between reproduction and somatic maintenance. DST predicts that investments in reproduction accentuate somatic damage which increase senescence and shortens lifespan. Here, we directly tested DST predictions in breeding and nonbre...

Golden Syrian hamsters (Mesocricetus auratus) are a well-established animal model for human infections with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) due to their susceptibility to SARS-CoV-2 infection, robust virus replication and pathological manifestations similar to human COVID-19 pneumonia. To investigate the physiological c...

Application of the physical laws of energy and mass conservation at the whole-body level is not necessarily informative about causal mechanisms of weight gain and the development of obesity. The energy balance model (EBM) and the carbohydrate-insulin model (CIM) are two plausible theories, among several others, attempting to explain why obesity dev...

Female soccer players have been identified as presenting with low energy availability (LEA), though the prevalence of LEA may be overestimated given inaccuracies associated with self‐reporting dietary intakes. Accordingly, we aimed to quantify total daily energy expenditure (TDEE) via the doubly labelled water (DLW) method, energy intake (EI) and e...

Rationale The precision of the doubly labeled water (DLW) method is determined by the precision and accuracy of the isotopic measurements. Quality control (QC) procedures to mitigate sample variability require additional measurements if sample duplicates differ more than a factor of instrument precision. We explored the effect of widening QC ranges...

Variations in physical activity energy expenditure can make accurate prediction of total energy expenditure (TEE) challenging. The purpose of the present study was to determine the accuracy of available equations to predict TEE in individuals varying in physical activity (PA) levels. TEE was measured by DLW in 56 adults varying in PA levels which w...

Caloric restriction (CR) results in reduced energy and protein intake, raising questions about protein restriction’s contribution to CR longevity benefits. We kept ad libitum (AL)–fed male C57BL/6J mice at 27°C (AL27) and pair-fed (PF) mice at 22°C (22(PF27)). The 22(PF27) group was fed to match AL27 while restricted for calories due to cold-induce...

Objectives We aimed to validate dietary assessment methods against the gold standard, doubly labeled water (DLW), for estimating total energy intake (TEI). Methods PubMed, Scopus, Web of Science, and Google Scholar databases were searched until May 2023. Inclusion criteria encompassed studies involving participants aged 1–18 years, employing dieta...

Objective High‐fat diets cause obesity in male mice; however, the underlying mechanisms remain controversial. Here, three contrasting ideas were assessed: hedonic overdrive, reverse causality, and passive overconsumption models. Method s A total of 12 groups of 20 individually housed 12‐week‐old C57BL/6 male mice were exposed to 12 high‐fat diets...

According to the heat dissipation limit (HDL) theory, reproductive performance is limited by the capacity to dissipate excess heat. We tested novel hypotheses that (1) the age-related decline in reproductive performance is due to age-related decrease of heat dissipation capacity and (2) that the limiting mechanism is more severe in animals with hig...

The trade off between energy gained and expended is the foundation of understanding how, why and when animals perform any activity. Based on the concept that animal movements have an energetic cost, accelerometry is increasingly being used to estimate energy expenditure. However, validation of accelerometry as an accurate proxy for field metabolic...

Early life nutrition can reprogram development and exert long‐term consequences on body weight regulation. In mice, maternal high‐fat diet (HFD) during lactation predisposed male but not female offspring to diet‐induced obesity when adult. Molecular and cellular changes in the hypothalamus at important time points are examined in the early postnata...

The limits to sustained energy intake set physiological upper boundaries that affect many aspects of human and animal performance. The mechanisms underlying these limits however remain unclear. We exposed Swiss mice to either supplementary thyroid hormones (THs) or methimazole during lactation at 21 °C or 32.5 °C, and measured food intake, resting...

There is considerably greater variation in metabolic rates between men than between women, in terms of basal, activity and total (daily) energy expenditure (EE). One possible explanation is that EE is associated with male sexual characteristics (which are known to vary more than other traits) such as musculature and athletic capacity. Such traits m...

Understanding aging is a key biological goal. Precision gerontology aims to predict how long individuals will live under different treatment scenarios. Calorie and protein restriction (CR and PR) extend lifespan in many species. Using data from C57BL/6 male mice under graded CR or PR, we introduce a computational thermodynamic model for entropy gen...

Body weight and fatness appear to be regulated phenomena. Several different theoretical models are available to capture the essence of this idea. These include the set-point, dynamic equilibrium, adiposity force, control theory-settling point, Hall–Guo, operation point and dual intervention point (DIP) models. The set-point model posits a single re...

Obesity is now a global pandemic, but there is little consensus about the causes.

This chapter describes the process of sexual reproduction in animals. Sexual reproduction involves the meeting of two specialized cells called gametes, one from each parent, normally of the same species. Fertilization occurs either within a female or in the surrounding environment, depending on the species. The chapter then differentiates between o...

This chapter focuses on how animals sense their environments. The world as perceived by animals is defined by their senses, which receive and interpret only a small fraction of the potential sensory information available in their environment. Each individual group of animals has evolved different sensory priorities and specific abilities to ensure...

This chapter assesses muscular systems and animal locomotion. Animal movement and behaviour in the environment is powered by the pulling force produced by contracting muscles. The contractile apparatus in all muscles consists of myofibrils made up of myosin-containing and actin-containing filaments. Contraction of voluntary muscles is under the dir...

This chapter explores temperature regulation in ectotherms. Almost all invertebrates, all amphibians, most fish, and most reptiles are ectotherms. Ectotherms influence their body temperatures by behavioural thermoregulation. The simplest form of behavioural thermoregulation is thermal selection according to the preferred body temperatures of aquati...

This chapter examines the environmental and behavioural influences on the cardiorespiratory systems of animals. Changes in the demand for and supply of oxygen are met by varying components of the respiratory and circulatory systems contained within the Fick principle of convection. Feeding and digestion lead to an increase in the rate of oxygen con...

This chapter examines the physical principles governing the movement of molecules, ions, and heat in biological systems, the general properties of animal cells, and their interactions with the extracellular environment. The ease with which substances can pass across a barrier is expressed by permeability constants, and the movement of ions across b...

This chapter explores the control of sodium, water, and calcium balance in animals. The renin–angiotensin system is the main regulator of aldosterone secretion; aldosterone is the main salt-conserving hormone of tetrapods. Aldosterone stimulates salt absorption from the distal nephron and fluids in various non-renal tissues: amphibian urinary bladd...

This chapter addresses the role of kidneys for excretion of waste in animals. It begins by looking at how animals produce the primary urine by secretion or ultrafiltration. The size and electrical charge of solutes determines their ultrafiltration by the vertebrate glomerulus via an extracellular route across the capillary endothelium, basement mem...

This chapter discusses energy metabolism in animals. It focuses on how animals meet their bodies' demands for energy and on the common processes involved in the flow of energy. This process starts with the acquisition of food and sees the transfer of energy from food to molecules of adenosine triphosphate (ATP), the common currency for energy trans...

This chapter evaluates body fluid regulation of animals. The bulk of the body mass of animals is water, distributed between intracellular fluid (ICF) inside the cells and extracellular fluid (ECF) outside the cells. In aquatic animals, the osmotic concentration of fluids on either side of their permeable external epithelia influences the rate of wa...

This chapter studies the integration of the respiratory and circulatory systems in animals. The activity of the respiratory pumps is produced within the central nervous system by a network of oscillating neurons: a central rhythm (pattern) generator. Meanwhile, the rhythmic activity of the circulatory pumps (hearts) is produced in most groups of an...

This chapter highlights respiratory systems of animals. Gas exchange occurs across the general body surface, gills, lungs or tracheoles. There are four basic types of gas-exchanger: infinite pool exchangers, countercurrent exchangers, ventilated pool gas-exchangers, and cross-current exchangers. Some species of animals that live in water but have a...

This chapter reviews the transport of the respiratory gases in the respiratory systems of animals. Two major respiratory pigments are found in the blood: the copper-based haemocyanin and the iron-based haemoglobin. The maximum concentration of oxygen in the blood when the blood pigment is fully saturated is the oxygen-carrying capacity. Meanwhile,...

This chapter evaluates the nervous systems in animals. All animals except Placozoa and Porifera (sponges) have a well-defined nervous system, which is the main means of communication between the animal and the outside world. Animals with bilateral symmetry have a central and a peripheral nervous system. The central nervous system (CNS) in invertebr...

Animal Physiology is composed of five parts. Part One looks at animals and their environment. It considers diversity and cells, organisms, and interactions. Part Two looks at water and salts including kidneys, excretion, water balance of land animals, and body fluid regulation. The text then goes on to examine issues related to temperature. It asks...

This chapter addresses the hormonal processes in animals. There are four sub-categories of chemical communication that operate in animals, and which are recognizable by the type of cell that produces the chemical and the distance over which the chemicals exert effects. These categories include neuroendocrine secretion of neurohormones synthesized a...

This chapter begins by setting out the scope of environmental animal physiology before discussing the range of environments and the challenges they pose for the animals that occupy them. Environmental animal psychology provides mechanistic explanations that help predict the impacts of environmental change on the most vulnerable species. Terrestrial...

This chapter describes the effects of temperature on biological functions to explain why all animals need to control their body temperature to a greater or lesser extent. The rate of a chemical reaction is directly proportional to the concentration of the reactant molecules and the proportionality constant is called the rate constant. As temperatur...

This chapter discusses the cardiovascular systems of animals. Most invertebrates have an open circulatory system, although decapod crustaceans and some species of non-cephalopod molluscs have an incompletely closed system. Vertebrates have a closed circulatory system: all blood vessels are lined with endothelium. In water-breathing invertebrates, t...

This chapter identifies the general characteristics of the respiratory gases and the principles underlying the processes involved in respiratory gas-exchange. When it was originally formed, about 4.5 billion years ago, the atmosphere of the Earth contained no oxygen. The subsequent changes in the concentration of oxygen in the atmosphere coincided...

This chapter focuses on osmotic and ionic regulation in aquatic animals. The osmotic and ionic concentrations of aquatic environments and their variability have profound implications for the salt and water balance of animals living in these habitats. Some marine invertebrates regulate the concentration of particular ions in extracellular fluids. Me...

This chapter studies temperature regulation in endotherms. Endotherms compensate for heat loss to their environment in order to maintain their body temperature several degrees above ambient. Animals decrease their thermal conductance to minimize their rate of heat loss. This can be achieved by erecting hairs or feathers to increase the insulating l...

This chapter assesses the major routes for water loss from land animals and the evolutionary adaptations that limit these water losses. Evaporative water loss (EWL) is driven by the difference in partial pressures of water vapour in the solution from which evaporation occurs and in the air surrounding an animal. Burrowing reduces EWL of some animal...

Purpose of review: Physical activity impacts energy balance because of its contribution to total energy expenditure. Measuring physical activity energy expenditure (PAEE) is often performed by subtracting the estimated 24 h expenditure on basal metabolism (called basal energy expenditure or BEE) from the total energy expenditure (TEE) measured by...

Caloric restriction that promotes weight loss is an effective strategy for treating non-alcoholic fatty liver disease and improving insulin sensitivity in people with type 2 diabetes¹. Despite its effectiveness, in most individuals, weight loss is usually not maintained partly due to physiological adaptations that suppress energy expenditure, a pro...

Calorie restriction (CR) typically promotes a reduction in body mass which correlates with increased lifespan. We evaluated the overall changes in survival, body mass dynamics, and body composition following long-term graded CR (580 days/19 months) in male C57BL/6J mice. Control mice (0% restriction) were fed ad libitum in the dark phase only (12AL...

Climate warming can reduce food resources for animal populations. In species exhibiting parental care, parental effort is a ‘barometer’ of changes in environmental conditions. A key issue is the extent to which variation in parental effort can buffer demographic rates against environmental change. Seabirds breed in large, dense colonies and globall...

Obesity is caused by a prolonged positive energy balance1,2. Whether reduced energy expenditure stemming from reduced activity levels contributes is debated3,4. Here we show that in both sexes, total energy expenditure (TEE) adjusted for body composition and age declined since the late 1980s, while adjusted activity energy expenditure increased ove...

Diet plays a substantial role in the etiology, progression, and treatment of chronic disease and is best considered as a multifaceted set of modifiable input variables with pleiotropic effects on a variety of biological pathways spanning multiple organ systems. This brief review discusses key issues related to the design and conduct of diet interve...

The assessment of total energy expenditure (TEE) is imperative to ensure appropriate fuelling during competition and training, although the current lack of TEE research in para sport make the prescription of nutritional strategies challenging. This study aimed to assess TEE of an elite wheelchair tennis (WT) player during training and competition o...

Heat waves are becoming more frequent across the globe and may impose severe thermoregulatory challenges for endotherms. Heat stress can induce both behavioral and physiological responses, which may result in energy deficits with potential fitness consequences. We studied the responses of reindeer (Rangifer tarandus tarandus), a cold-adapted ungula...

Understanding how birds annually allocate energy to cope with changing environmental conditions and physiological states is a fundamental question in avian ecology. The two main hypotheses to explain annual patterns in energy use are "reallocation" and "increased demand". The reallocation hypothesis suggests equal energetic costs in winter and bree...

Objective: Obesity in laboratory rodents is generally induced by feeding them a high fat diet (HFD). This model does not permit separation of the impact of the HFD from the resultant obesity on metabolic defects such as impaired glucose homeostasis. In Brandt's voles we have previously shown that exposure to long photoperiod (LD: 16L: 8D) induces...

Purpose: An understanding of an athlete's total daily energy expenditure (TEE) is necessary to inform nutritional strategies, particularly where daily training and competitive demands are highly variable. This observational case series assessed the TEE of elite tennis players during high-level competition. Methods: Senior female singles particip...

The European Food Safety Authority has suggested that EU countries implement the 2x24-hour diet recall (2x24hDR) method and physical activity (PA) measurements for national dietary surveys. Since 2000, Denmark has used 7-day Food Diaries (7dFD) with PA questionnaires and measurements. The accuracy of the two diet and PA methods was evaluated by com...

Calorie restriction (CR) extends lifespan by modulating the mechanisms involved in aging. We quantified the hepatic proteome of male C57BL/6 mice exposed to graded levels of CR (0% to 40% CR) for three months, and evaluated which signaling pathways were most affected. The metabolic pathways most significantly stimulated by the increase in CR, inclu...

Obesity remains an unmet global health burden. Detrimental anatomical distribution of body fat is a major driver of obesity-mediated mortality risk and is demonstrably heritable. However, our understanding of the full genetic contribution to human adiposity is incomplete, as few studies measure adiposity directly. To address this, we impute whole-b...

Peak lactation occurs when milk production is at its highest. The factors limiting peak lactation performance have been subject of intense debate. Milk production at peak lactation appears limited by the capacity of lactating females to dissipate body heat generated as a by-product of processing food and producing milk. As a result, manipulations t...

Water is essential for survival, but one in three individuals worldwide (2.2 billion people) lacks access to safe drinking water. Water intake requirements largely reflect water turnover (WT), the water used by the body each day. We investigated the determinants of human WT in 5604 people from the ages of 8 days to 96 years from 23 countries using...

[This corrects the article DOI: 10.3389/fnut.2022.835536.].

In mammals, trait variation is often reported to be greater among males than females. However, to date, mainly only morphological traits have been studied. Energy expenditure represents the metabolic costs of multiple physical, physiological, and behavioral traits. Energy expenditure could exhibit particularly high greater male variation through a...