John Speakman

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

PhD DSc
researching human and animal energy balance

About

811
Publications
257,727
Reads
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38,828
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Introduction
I run two research groups: one at SIAT in Shenzhen, China, and one in Aberdeen, Scotland. My work focuses on energy balance - the factors that govern variation in food intake and energy expenditure, and the consequences for fat storage (obesity) and ageing. This includes studies in free-living and captive animals, and humans. Our work stretches from the gene to the individual. We have particular expertise in use of doubly-labelled water to measure energy demands.
Additional affiliations
August 2020 - May 2021
Chinese Academy of Sciences
Position
  • Principal Investigator
September 2011 - December 2021
Chinese Academy of Sciences
Position
  • Professor
January 1985 - December 2024
University of Aberdeen
Position
  • Professor (Full)
Education
September 2010 - June 2017
The Open University
Field of study
  • Maths and Statistics
June 2000 - June 2009
University of Stirling
Field of study
  • Biology
October 1991 - June 1997
University of Aberdeen
Field of study
  • Biology

Publications

Publications (811)
Article
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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...
Article
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...
Article
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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.
Article
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...
Article
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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...
Article
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Background: Considerable attention is currently focused on the potential to switch on brown adipose tissue (BAT), or promote browning of white adipose tissue, to elevate energy expenditure and thereby reduce obesity levels. These processes are already known to be switched on by cold exposure. Yet humans living in colder regions do not show lower l...
Article
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Lower ambient temperature (Ta) requires greater energy expenditure to sustain body temperature. However, effects of Ta on human energetics may be buffered by environmental modification and behavioral compensation. We used the IAEA DLW database for adults in the USA (n = 3213) to determine the effect of Ta (-10 to +30°C) on TEE, basal (BEE) and acti...
Article
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Background: Consumption of meals bought from out-of-home sources is a suggested risk factor for obesity, but the supporting evidence is mixed. Objectives: To investigate the association between consumption of different types of meals and BMI or percent body fat. Methods: Data were from the UK Biobank in response to a "Type of Meals Eaten" surv...
Article
Calorie restriction (CR) without malnutrition increases the health- and lifespan of diverse taxa. The mechanism(s) behind CR are debated but may be directly linked to body composition changes that maintain energy balance. During a deficit, energy is primarily obtained from white adipose tissue (WAT; utilized) whilst other tissues remain unchanged (...
Article
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Caloric restriction is a robust intervention to increase lifespan. Giving less food (calorie restriction [CR]) or allowing free access to a diluted diet with indigestible components (calorie dilution [CD]) are two methods to impose restriction. CD does not generate the same lifespan effect as CR. We compare responses of C57BL/6 mice with equivalent...
Article
People completely lacking body fat (lipodystrophy/lipoatrophy), and those with severe obesity, both show profound metabolic and other health issues. Regulating levels of body fat somewhere between these limits would therefore appear to be adaptive. Two different models might be contemplated. More traditional is a set-point where levels are regulate...
Article
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Dietary macronutrient composition influences both hepatic function and aging. Previous work suggested that longevity and hepatic gene expression levels were highly responsive to dietary protein, but almost unaffected by other macronutrients. In contrast, we found expression of 4005, 4232, and 4292 genes in the livers of mice were significantly asso...
Article
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A variety of inbred mouse strains have been used for research in metabolic disorders. Despite being inbred, they display large inter-individual variability for many traits like food intake and body weight. However, the relationship between dietary macronutrients and inter-individual variation in body weight and food intake of different mouse strain...
Article
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The relationships between metabolic rate, body temperature (Tb), body composition and ageing are complex, and not fully resolved. In particular, Tb and metabolic rate often change in parallel, making disentangling their effects difficult. Here we show that in both sexes of mice and hamsters exposure to a temperature of 32.5 °C leads to a reduced li...
Chapter
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Temperature has a profound effect on many aspects of murine physiology. This raises the question of the best temperature at which mice should be housed to maximize the translational potential to humans. The temperatures at which mice have been routinely kept for studies of molecular physiology (20–21 °C) maximize the comfort of animal handling staf...
Article
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Patterns in functional diversity of organisms at large spatial scales can provide insight into possible responses to future climate change, but it remains a challenge to link large-scale patterns at the population or species level to their underlying physiological mechanisms at the individual level. The climate variability hypothesis predicts that...
Article
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Food intake is generally assumed to reflect a regulatory tension between homeostatic and hedonic drivers. Information from individuals with memory dysfunction suggests that episodic memory may also play a significant role. We reasoned that if memory influences food intake, then disrupting a genetic factor that is important in episodic memory format...
Article
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Objectives The link between excess adiposity and left ventricular hypertrophy is multifaceted with sparse data among youths. Given that adipokines/hepatokines may influence lipid metabolism in myocardium, we aimed to investigate the relation of the novel hepatokine angiopoietin-like protein 8 (ANGPTL8) and other adipokines with cardiac structure in...
Article
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Low total energy expenditure (TEE, MJ/d) has been a hypothesized risk factor for weight gain, but repeatability of TEE, a critical variable in longitudinal studies of energy balance, is understudied. We examine repeated doubly labeled water (DLW) measurements of TEE in 348 adults and 47 children from the IAEA DLW Database (mean ± SD time interval:...
Article
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Purpose: To quantify total daily energy expenditure (TEE) of international adult female soccer players. Methods: Twenty-four professional players were studied during a twelve-day period where they participated in an international training camp (also inclusive of two competitive games) representing the English national team. TEE was assessed via...
Article
Dietary choices have a profound impact on the aging process. In addition to the total amount of energy intake, macronutrient composition influences both health and lifespan. However, the exact mechanisms by which dietary macronutrients influence onset and progression of age-associated features remain poorly understood. Cellular senescence is a stat...
Article
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Background: The United Kingdom (UK) implemented several national lockdowns during the coronavirus pandemic during which restaurants were closed and people were advised to stay at home if possible. These restrictions were eased and reapplied multiple times between March 2020 and May 2021. The change in restaurant access and prolonged restriction of...
Article
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Objective Maternal high-fat diet (HFD) increases offspring obesity, yet the impacts of different levels of maternal dietary fat have seldom been addressed. In mice, the impact of graded maternal dietary fat on offspring adiposity and offspring’s later susceptibility to HFD were assessed. Methods Lactating mice were fed diets with graded fat cont...
Article
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We investigated the effects of environmental factors on average daily milk yield and day-to-day variation in milk yield of barn-housed Scottish dairy cows milked with an automated milking system. An incomplete Wood gamma function was fitted to derive parameters describing the milk yield curve including initial milk yield, inclining slope, declining...
Article
Over-consumption of calories rather than decreased expenditure is the most likely cause of the obesity epidemic. The reasons for this remain disputed with all the main macro-nutrients (fat, protein and carbohydrate) being implicated by different authors. Stimulated intake by declining dietary protein (protein leverage) may be important. The carbohy...
Article
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Gut microorganisms not only participate in the metabolism of carbohydrate, lipids, protein, and polypeptides in the intestine but also directly affect the metabolic phenotypes of the host. Although many studies have described the apparent effects of gut microbiota on human health, the development of metagenomics and culturomics in the past decade h...
Article
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Background: Physical activity may be a way to increase and maintain fat-free mass (FFM) in later life, similar to the prevention of fractures by increasing peak bone mass. Objectives: A study is presented of the association between FFM and physical activity in relation to age. Methods: In a cross-sectional study, FFM was analyzed in relation t...
Article
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A lifetime of change Measurements of total and basal energy in a large cohort of subjects at ages spanning from before birth to old age document distinct changes that occur during a human lifetime. Pontzer et al . report that energy expenditure (adjusted for weight) in neonates was like that of adults but increased substantially in the first year o...
Article
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Gut microbiota deficient mice demonstrate accelerated glucose clearance. However, which tissues are responsible for the upregulated glucose uptake remains unresolved, with different studies suggesting that browning of white adipose tissue, or modulated hepatic gluconeogenesis, may be related to enhanced glucose clearance when the gut microbiota is...
Article
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Significance Caloric restriction (CR) increases life and health span, but our understanding of the evolutionary basis of the effect remains unclear. For many years, the disposable soma hypothesis provided the main evolutionary explanation, suggesting animals under restriction divert resources away from reproduction toward somatic maintenance. This...
Article
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Understanding the impacts of activity on energy balance is crucial. Increasing levels of activity may bring diminishing returns in energy expenditure because of compensatory responses in non-activity energy expenditures.1, 2, 3 This suggestion has profound implications for both the evolution of metabolism and human health. It implies that a long-te...
Article
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Significance Endothermic animals must survive periods of seasonally lowered temperature, coincident with lowered food supply. While we know much about hibernation and migration as survival strategies, the responses of nonhibernating, nonmigrating species are more opaque, yet how these animals survive such periods is important to understand their po...
Article
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The giant panda (Ailuropoda melanoleuca) is an iconic bear native to China, famous for eating almost exclusively bamboo. This unusual dietary behavior for a carnivore is enabled by several key adaptations including low physical activity, reduced organ sizes and hypothyroidism leading to lowered energy expenditure. These adaptive phenotypes have bee...
Article
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Seasonal energetic challenges may constrain an animal's ability to respond to changing individual and environmental conditions. Here, we investigated variation in heart rate, a well-established proxy for metabolic rate, in Svalbard reindeer ( Rangifer tarandus platyrhynchus ), a species with strong seasonal changes in foraging and metabolic activit...
Article
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Whey protein isolate (WPI) is considered a dietary solution to obesity. However, the exact mechanism of WPI action is still poorly understood but is probably connected to its beneficial effect on energy balance, adiposity, and metabolism. More recently its ability to modulate the gut microbiota has received increasing attention. Here, we used a mic...
Article
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(Cell Metabolism 33, 888–904.e1–e6; May 4, 2021) In the original version of the article's Figure 7, the Figures 7P and 7O are the same. We mistakenly duplicated the figure 7P during the production process. This error has been corrected online. As this error occurred in figure production and not during data analysis, this error has no impact on the...
Article
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Insulin plays a role in body fat regulation independent of dietary carbohydrates
Article
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Commercial saturation divers are exposed to unique environmental conditions and are required to conduct work activity underwater. Consequently, divers' physiological status is shown to be perturbed and therefore, appropriate strategies and guidance are required to manage the stress and adaptive response. This study aimed to evaluate the daily energ...
Article
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We investigated how protein quantity (10%–30%) and quality (casein and whey) interact with dietary fat (20%–55%) to affect metabolic health in adult mice. Although dietary fat was the main driver of body weight gain and individual tissue weight, high (30%) casein intake accentuated and high whey intake reduced the negative metabolic aspects of high...
Preprint
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Daily water intake (DWI) is essential for survival in humans; however, accurate assessment of DWI from drinks and beverages (Wdrinks) or food moisture (Wfoods) is difficult as it depends on self-reported intakes that are prone to inaccuracy. Here, we established an objective method to assess DWI components using doubly labeled water (DLW). Deuteriu...
Article
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The fasting endurance hypothesis (FEH) predicts strong selection for large body size in mammals living in environments where food supply is interrupted over prolonged periods of time. The Arctic is a highly seasonal and food restricted environment, but contrary to predictions from the FEH, empirical evidence shows that Arctic mammals are often smal...
Article
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Activation of an immune response (IR) upon exposure to pathogens is crucial to ensure adequate organismal performance and is directly linked to survival. Fitness benefits of the response may be associated with costs in terms of increased energy expenditure and may compete for resources and compromise such fitness benefits. Trade‐offs between immune...
Article
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Understanding energy use is central to understanding an animal's physiological and behavioural ecology. However, directly measuring energy expenditure in free-ranging animals is inherently difficult. The doubly-labelled water (DLW) method is widely used to investigate energy expenditure in a range of taxa. Although reliable, DLW data collection and...
Article
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The doubly labeled water (DLW) method measures total energy expenditure (TEE) in free-living subjects. Several equations are used to convert isotopic data into TEE. Using the International Atomic Energy Agency (IAEA) DLW database (5,756 measurements of adults and children), we show considerable variability is introduced by different equations. The...
Article
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Many captive Asian elephant populations are not self-sustaining, possibly due in part to obesity-related health and reproductive issues. This study investigated relationships between estimated body composition and metabolic function, inflammatory markers, ovarian activity (females only) and physical activity levels in 44 Asian elephants ( n =35 fem...
Article
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Laying hens are increasingly kept in barn or free-range systems, which not only allows birds to move freely but also potentially entails higher energy expenditures due to higher locomotor activity. Therefore, the aim of our study was to quantify the daily energy expenditure (DEE) and water turnover in freely moving laying hens. For that purpose, 10...
Article
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Many countries implemented various levels of lockdown to mitigate spread of the global Sars‐Cov‐2 pandemic. In the UK, the lockdown restrictions were implemented nationally between 26th March and 4th July 2020. They required all restaurants to close except for takeaway and delivery services. Moreover, individuals were instructed to largely stay in...
Article
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Elite human and animal athletes must acquire the fuels necessary for extreme feats, but also contend with the oxidative damage associated with peak metabolic performance. Here, we show that a migratory bird with fuel stores composed of more omega-6 polyunsaturated fats (PUFA) expended 11% less energy during long-duration (6 hr) flights with no chan...
Article
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Energy drives behaviour and life history decisions, yet it can be hard to measure at fine scales in free-moving animals. Accelerometry has proven a powerful tool to estimate energy expenditure, but requires calibration in the wild. This can be difficult in some environments, or for particular behaviours, and validations have produced equivocal resu...
Article
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Golden hamsters have four times the body size of mice, raise very large litters and are required to produce big quantities of milk during the 18 days lactation period. We have previously proposed that they may be prone to being limited by their heat dissipation capacity. Studies where lactating females are shaved to elevate their heat dissipation c...
Article
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Calorie restriction (CR) remains the most robust intervention to extend lifespan and improve healthspan. Though the cerebellum is more commonly associated with motor control, it has strong links with the hypothalamus and is thought to be associated with nutritional regulation and adiposity. Using a global mass spectrometry-based metabolomics approa...
Article
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Significance Models of future climate change have tended to focus on changes in average temperature, which in physiological terms are relatively trivial. Of more physiological importance is the future elevated risk of heat waves. We show here that during peak lactation in two species of small rodent the upper lethal temperature is reduced by around...
Article
Background and aims: Future climate change may adversely impact human health. The direct effects of extreme hot temperatures on mortality are well established, and their future impact well modelled. However, less extreme changes in ambient temperature (Ta) have been previously associated with increased mortality from circulatory and metabolic dise...
Article
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Background: The frequency of visits to restaurants has been suggested to contribute to the pandemic of obesity. However, few studies have examined how individual use of these restaurants is related to Body Mass Index (BMI). Aim: To investigate the association between the usage of different types of food outlets and BMI among adults in Scotland....