Protein Leverage: Theoretical Foundations and Ten Points of Clarification

Mice Regulate Dietary Amino Acid Balance and Energy Intake by Selecting between Complementary Protein Sources

BACKGROUND

A balanced intake of protein and constituent amino acids (AAs) requires adjustments to total food intake (protein leverage [PL]) and food selection to balance deficits and excesses (complementary feeding). We provided mice with choices of casein and whey, 2 protein sources that are complementary in AA balance, across a range of protein concentrations (P%) of digestible energy (DE).

OBJECTIVES

We aimed to determine if: 1) PL operates similarly for casein and whey; 2) one protein source is preferred at control P%; 3) the preference changes as P% falls; and 4) AA intakes under control and low P% levels identify AAs that drive changes in protein selection.

METHODS

Food intake and plasma fibroblast growth factor-21 (FGF21) concentrations were measured in mice at various P% (P7.5%-P33%). For direct comparisons, defined diets were used in which the protein source was either casein or whey. In food choice studies, mice had access to foods in which both casein and whey were provided at the same P% level at the same time.

RESULTS

PL operated at different P% thresholds in casein (13%)- and whey (10%)-based diets, and the magnitude of PL was greater for casein. Although mice preferred casein under control conditions (P23%), a pronounced preference shift to whey occurred as P% fell to P13% and P10%. At low P%, increases in food intake were accompanied by increases in plasma FGF21, a protein hunger signal. Among AAs deficient in casein and enriched in whey, the intake of Cys was the most invariant as P% changed between P23% and P10%, appearing to drive the switch in protein preference.

CONCLUSIONS

Mice selected between complementary protein sources, casein and whey, achieving stable total energy intake and regulated intake of AAs as P% varied. Supplementation of low P% casein diets with one whey-enriched AA, Cys, suppressed plasma FGF21 and total food intake.

Post-natal muscle growth and protein turnover: a narrative review of current understanding

A model explaining the dietary-protein-driven post-natal skeletal muscle growth and protein turnover in the rat is updated, and the mechanisms involved are described, in this narrative review. Dietary protein controls both bone length and muscle growth, which are interrelated through mechanotransduction mechanisms with muscle growth induced both from stretching subsequent to bone length growth and from internal work against gravity. This induces satellite cell activation, myogenesis and remodelling of the extracellular matrix, establishing a growth capacity for myofibre length and cross-sectional area. Protein deposition within this capacity is enabled by adequate dietary protein and other key nutrients. After briefly reviewing the experimental animal origins of the growth model, key concepts and processes important for growth are reviewed. These include the growth in number and size of the myonuclear domain, satellite cell activity during post-natal development and the autocrine/paracrine action of IGF-1. Regulatory and signalling pathways reviewed include developmental mechanotransduction, signalling through the insulin/IGF-1-PI3K-Akt and the Ras-MAPK pathways in the myofibre and during mechanotransduction of satellite cells. Likely pathways activated by maximal-intensity muscle contractions are highlighted and the regulation of the capacity for protein synthesis in terms of ribosome assembly and the translational regulation of 5-TOPmRNA classes by mTORC1 and LARP1 are discussed. Evidence for and potential mechanisms by which volume limitation of muscle growth can occur which would limit protein deposition within the myofibre are reviewed. An understanding of how muscle growth is achieved allows better nutritional management of its growth in health and disease.

FGF21 acts in the brain to drive macronutrient-specific changes in behavioral motivation and brain reward signaling

Dietary protein restriction induces adaptive changes in food preference, increasing protein consumption over carbohydrates or fat. We investigated whether motivation and reward signaling underpin these preferences. In an operant task, protein-restricted male mice increased their responding for liquid protein rewards, but not carbohydrate, fat, or sweet rewards. The protein restriction-induced increase in operant responding for protein was absent in Fgf21-KO mice and mice with neuron-specific deletion of the FGF21 co-receptor beta-Klotho (KlbCam2ka) mice. Fiber photometry recording of VTA dopamine neurons revealed that oral delivery of maltodextrin triggered a larger activation of dopamine neurons as compared to casein in control-fed mice, while casein produced a larger response in protein-restricted mice. This restriction-induced shift in nutrient-specific VTA dopamine signaling was lost in Fgf21-KO mice. These data demonstrate that FGF21 acts in the brain to induce a protein-specific appetite by specifically enhancing the reward value of protein-containing foods and the motivation to consume them.

Evidence for protein leverage on total energy intake, but not body mass index, in a large cohort of older adults

BACKGROUND

Protein leverage (PL) is the phenomenon of consuming food until absolute intake of protein approaches a 'target value', such that total energy intake (TEI) varies passively with the ratio of protein: non-protein energy (fat + carbohydrate) in the diet. The PL hypothesis (PLH) suggests that the dilution of protein in energy-dense foods, particularly those rich in carbohydrates and fats, combines with protein leverage to contribute to the global obesity epidemic. Evidence for PL has been reported in younger adults, children and adolescents. This study aimed to test for PL and the protein leverage hypothesis (PLH) in a cohort of older adults.

METHODS

We conducted a retrospective analysis of dietary intake in a cohort of 1699 community-dwelling older adults aged 67-84 years from the NuAge cohort. We computed TEI and the energy contribution (EC) from each macronutrient. The strength of leverage of macronutrients was assessed through power functions ( TEI = μ * EC L ). Body mass index (BMI) was calculated, and mixture models were fitted to predict TEI and BMI from macronutrients' ECs.

RESULTS

In this cohort of older adults, 53% of individuals had obesity and 1.5% had severe cases. The mean TEI was 7673 kJ and macronutrients' ECs were 50.4%, 33.2% and 16.4%, respectively for carbohydrates, fat, and protein. There was a strong negative association (L = -0.37; p < 0.001) between the protein EC and TEI. Each percent of energy intake from protein reduced TEI by 77 kJ on average, ceteris paribus. However, BMI was unassociated with TEI in this cohort.

CONCLUSIONS

Findings indicate clear evidence for PL on TEI, but not on BMI, likely because of aging, body composition, sarcopenia, or protein wasting.

Paternal dietary macronutrient balance and energy intake drive metabolic and behavioral differences among offspring

Paternal diet can influence the phenotype of the next generation, yet, the dietary components inducing specific responses in the offspring are not identified. Here, we use the Nutritional Geometry Framework to determine the effects of pre-conception paternal dietary macronutrient balance on offspring metabolic and behavioral traits in mice. Ten isocaloric diets varying in the relative proportion of protein, fats, and carbohydrates are fed to male mice prior to mating. Dams and offspring are fed standard chow and never exposed to treatment diets. Body fat in female offspring is positively associated with the paternal consumption of fat, while in male offspring, an anxiety-like phenotype is associated to paternal diets low in protein and high in carbohydrates. Our study uncovers that the nature and the magnitude of paternal effects are driven by interactions between macronutrient balance and energy intake and are not solely the result of over- or undernutrition.

Maternal macronutrient intake effects on offspring macronutrient targets and metabolism

OBJECTIVE

Exposure in utero to maternal diet can program offspring health and susceptibility to disease. Using C57BL6/JArc mice, we investigated how maternal dietary protein to carbohydrate balance influences male and female offspring appetite and metabolic health.

METHODS

Dams were placed on either a low-protein (LP) or high-protein (HP) diet. Male and female offspring were placed on a food choice experiment post weaning and were then constrained to either a standard diet or Western diet. Food intake, body weight, and composition were measured, and various metabolic tests were performed at different timepoints.

RESULTS

Offspring from mothers fed HP diets selected a higher protein intake and had increased body weight in early life relative to offspring from LP diet-fed dams. As predicted by protein leverage theory, higher protein intake targets led to increased food intake when offspring were placed on no-choice diets, resulting in greater body weight and fat mass. The combination of an HP maternal diet and a Western diet further exacerbated this obesity phenotype and led to long-term consequences for body composition and metabolism.

CONCLUSIONS

This work could help explain the association between elevated protein intake in humans during early life and increased risk of obesity in childhood and later life.

Short-term hypercaloric carbohydrate loading increases surgical stress resilience by inducing FGF21

Dietary restriction promotes resistance to surgical stress in multiple organisms. Counterintuitively, current medical protocols recommend short-term carbohydrate-rich drinks (carbohydrate loading) prior to surgery, part of a multimodal perioperative care pathway designed to enhance surgical recovery. Despite widespread clinical use, preclinical and mechanistic studies on carbohydrate loading in surgical contexts are lacking. Here we demonstrate in ad libitum-fed mice that liquid carbohydrate loading for one week drives reductions in solid food intake, while nearly doubling total caloric intake. Similarly, in humans, simple carbohydrate intake is inversely correlated with dietary protein intake. Carbohydrate loading-induced protein dilution increases expression of hepatic fibroblast growth factor 21 (FGF21) independent of caloric intake, resulting in protection in two models of surgical stress: renal and hepatic ischemia-reperfusion injury. The protection is consistent across male, female, and aged mice. In vivo, amino acid add-back or genetic FGF21 deletion blocks carbohydrate loading-mediated protection from ischemia-reperfusion injury. Finally, carbohydrate loading induction of FGF21 is associated with the induction of the canonical integrated stress response (ATF3/4, NF-kB), and oxidative metabolism (PPARγ). Together, these data support carbohydrate loading drinks prior to surgery and reveal an essential role of protein dilution via FGF21.

Comparative evaluation of milk proteins and oil-seed-cake-derived proteins extracted by chemical and biological methods for obesity management

BACKGROUND

In light of the exponential rise in global population, there is a critical requirement to reduce food waste on a global scale. According to studies, agricultural wastes such as oil-seed cakes offer great nutritional value. Acid precipitation (A) and alkaline extraction methods (traditional methods) were used to extract protein from oil-seed cakes; however, both procedures are linked to decreased protein quality and quantity, which prompted the development of a novel strategy known as the biological/microbial/probiotic (B) method. Therefore, the present study aimed to highlight the optimal way of protein extraction from oil-seed cakes and the effect of extraction methods on protein efficacy against obesity. The outcomes were also compared with milk proteins.

RESULTS

In vitro study provided evidence that proteins from both sources (plant and milk) suppressed adipogenesis and stimulated adipolysis in 3T3L-1 cells. For the in vivo study, mice were fed with different protein extracts: soya protein preparation (SPP), ground protein preparation (GPP), whey protein (WP) and casein protein (CP) containing 40% of their calories as fat. Body weight decreased significantly in all the rats except CP-fed rats. Body mass index, atherogenic index, plasma triglyceride and very-low-density lipoprotein cholesterol level decreased significantly in all the groups in comparison to the model group (high-fat-diet group), but the decrease was more pronounced in plant proteins than milk proteins. In hepatocytes, the expression of fasting-induced adipose factor, carnitine palmitoyltransferase I and peroxisome proliferator-activated receptor α genes was increased significantly in SPP-fed groups. Adiponectin gene expression was upregulated significantly in visceral fat tissue in groups fed SPP-B, GPP-A and CP, whereas leptin gene was downregulated significantly in all groups except SPP-A.

CONCLUSION

This study demonstrates that SPP-B showed the most effective anti-obesity property, followed by WP. Additionally, we found that the biological precipitation approach produced better outcomes for plant proteins isolated from oil-seed cakes than the acid precipitation method. © 2023 Society of Chemical Industry.

The fructose survival hypothesis as a mechanism for unifying the various obesity hypotheses

The pathogenesis of obesity remains contested. Although genetics is important, the rapid rise in obesity with Western culture and diet suggests an environmental component. Today, some of the major hypotheses for obesity include the energy balance hypothesis, the carbohydrate-insulin model, the protein-leverage hypothesis, and the seed oil hypothesis. Each hypothesis has its own support, creating controversy over their respective roles in driving obesity. Here we propose that all hypotheses are largely correct and can be unified by another dietary hypothesis, the fructose survival hypothesis. Fructose is unique in resetting ATP levels to a lower level in the cell as a consequence of suppressing mitochondrial function, while blocking the replacement of ATP from fat. The low intracellular ATP levels result in carbohydrate-dependent hunger, impaired satiety (leptin resistance), and metabolic effects that result in the increased intake of energy-dense fats. This hypothesis emphasizes the unique role of carbohydrates in stimulating intake while fat provides the main source of energy. Thus, obesity is a disorder of energy metabolism, in which there is low usable energy (ATP) in the setting of elevated total energy. This leads to metabolic effects independent of excess energy while the excess energy drives weight gain.

Associations between protein to non-protein ratio and intakes of other dietary components in a cohort aged 65-75 years: the Nutrition for Healthy Living Study

OBJECTIVE

Diets with a low proportion of energy from protein have shown to cause overconsumption of non-protein energy, known as Protein Leverage. Older adults are susceptible to nutritional inadequacy. The aim was to investigate associations between protein to non-protein ratio (P:NP) and intakes of dietary components and assess the nutritional adequacy of individuals aged 65-75 years from the Nutrition for Healthy Living (NHL) Study.

DESIGN

Cross-sectional. Nutritional intakes from seven-day weighed food records were compared with the Nutrient Reference Values for Australia and New Zealand, Australian Guide to Healthy Eating, Australian Dietary Guidelines and World Health Organisation Free Sugar Guidelines. Associations between P:NP and intakes of dietary components were assessed through linear regression analyses.

SETTING

NHL Study.

PARTICIPANTS

113 participants.

RESULTS

Eighty-eight (59 female and 29 male) with plausible dietary data had a median (interquartile range) age of 69 years (67-71), high education level (86 %) and sources of income apart from the age pension (81 %). Substantial proportions had intakes below recommendations for dairy and alternatives (89 %), wholegrain (89 %) and simultaneously exceeded recommendations for discretionary foods (100 %) and saturated fat (92 %). In adjusted analyses, P:NP (per 1 % increment) was associated with lower intakes of energy, saturated fat, free sugar and discretionary foods and higher intakes of vitamin B12, Zn, meat and alternatives, red meat, poultry and wholegrain % (all P < 0·05).

CONCLUSIONS

Higher P:NP was associated with lower intakes of energy, saturated fat, free sugar and discretionary. Our study revealed substantial nutritional inadequacy in this group of higher socio-economic individuals aged 65-75 years.

Branched-chain amino acids prevent obesity by inhibiting the cell cycle in an NADPH-FTO-m6A coordinated manner

Obesity has become a major health crisis in the past decades. Branched-chain amino acids (BCAA), a class of essential amino acids, exerted beneficial health effects with regard to obesity and its related metabolic dysfunction, although the underlying reason is unknown. Here, we show that BCAA supplementation alleviates high-fat diet (HFD)-induced obesity and insulin resistance in mice and inhibits adipogenesis in 3T3-L1 cells. Further, we find that BCAA prevent the mitotic clonal expansion (MCE) of preadipocytes by reducing cyclin A2 (CCNA2) and cyclin-dependent kinase 2 (CDK2) expression. Mechanistically, BCAA decrease the concentration of nicotinamide adenine dinucleotide phosphate (NADPH) in adipose tissue and 3T3-L1 cells by reducing glucose-6-phosphate dehydrogenase (G6PD) expression. The reduced NADPH attenuates the expression of fat mass and obesity-associated (FTO) protein, a well-known m6A demethylase, to increase the N6-methyladenosine (m6A) levels of Ccna2 and Cdk2 mRNA. Meanwhile, the high m6A levels of Ccna2 and Cdk2 mRNA are recognized by YTH N6-methyladenosine RNA binding protein 2 (YTHDF2), which results in mRNA decay and reduction of their protein expressions. Overall, our data demonstrate that BCAA inhibit obesity and adipogenesis by reducing CDK2 and CCNA2 expression via an NADPH-FTO-m6A coordinated manner in vivo and in vitro, which raises a new perspective on the role of m6A in the BCAA regulation of obesity and adipogenesis.

Nutritional, environmental and economic impacts of ultra-processed food consumption in Australia

OBJECTIVE

To quantify the full life cycle impacts of ultra-processed foods (UPF) for key environmental, economic and nutritional indicators to identify trade-offs between UPF contribution to broad-scope sustainability.

DESIGN

Using 24-h dietary recalls along with an input-output database for the Australian economy, dietary environmental and economic impacts were quantified in this national representative cross-sectional analysis. Food items were classified into non-UPF and UPF using the NOVA system, and dietary energy contribution from non-UPF and UPF fractions in diets was estimated. Thereafter, associations between nutritional, environmental and economic impacts of non-UPF and UPF fractions of diets were examined using a multi-dimensional nutritional geometry representation.

SETTING

National Nutrition and Physical Activity Survey 2011-2012 of Australia.

PARTICIPANTS

Respondents (n 5344) aged > 18 years with 1 d of 24-h dietary recall data excluding respondents with missing values and outlier data points and under reporters.

RESULTS

Australian diets rich in UPF were associated with reduced nutritional quality, high greenhouse gas emissions, energy use, and increased employment and income associated with the food supply chains. The environmental and economic impacts associated with the UPF portion of diets become more distinct when the diets are standardised to average protein recommendation.

CONCLUSION

Increased consumption of UPF has socio-economic benefits, but this comes with adverse effects on the environment and public health. Consideration of such trade-offs is important in identifying policy and other mechanisms regarding UPF for establishing healthy and sustainable food systems.

Effects of Diet Macronutrient Composition on Weight Loss during Caloric Restriction and Subsequent Weight Regain during Refeeding in Aging Mice

Caloric restriction (CR) induces weight loss, but is associated with rapid weight regain upon return to ad libitum feeding. Our aim was to investigate effects of the macronutrient composition of the diet on weight loss and regain in elderly mice. Males, 18 months old, of the C57BL/6J strain were subjected to 4-week 30% CR followed by 4 weeks of ad libitum refeeding on either high-carb (HC), high-fat (HF) or high-protein (HP) diets (n = 22 each). Mice (n = 11) fed a chow diet ad libitum served as a control group (CON). Body mass and food intake were monitored daily. Twenty-four-hour indirect calorimetry was used to assess energy expenditure and substrate oxidation. Muscle and fat mass were evaluated with dissection of the tissues. Serum leptin and ghrelin levels were also measured. CR-induced weight loss did not differ between the diets. Weight regain was particularly fast for HF as mice overshot their initial weight by 12.8 ± 5.7% after 4-week refeeding when HC and HP mice reached the weight of the CON group. Weight regain strongly correlated with energy intake across the groups. The respiratory exchange ratio was lower in HF mice (0.81 ± 0.03) compared to HC (0.94 ± 0.06, p < 0.001), HP (0.89 ± 0.04, p < 0.001) and CON mice (0.91 ± 0.06, p < 0.01) during the refeeding. Serum leptin levels were higher in HF mice (1.03 ± 0.50 ng/mL) compared to HC (0.46 ± 0.14, p < 0.001), HP (0.63 ± 0.28, p < 0.05) or CON mice (0.41 ± 0.14, p < 0.001). Thus, CR induces similar weight loss in aging mice irrespective of the diet's macronutrient composition. An HF diet leads to excessive energy intake and pronounced gain in body fat in spite of increased fat oxidation and serum leptin during the refeeding after CR.

Amino acid supplementation counteracts negative effects of low protein diets on tail biting in pigs more than extra environmental enrichment

Low protein (LP) diets may increase the occurrence of damaging behaviours, like tail biting, in pigs. We investigated the effect of supplementing a LP diet with indispensable amino acids (IAA) or environmental enrichment on tail biting. Undocked pigs (n = 48 groups of 12) received either a normal protein diet (NP), a LP, LP with supplemented IAA (LP+), or LP diet with extra environmental enrichment (LP-E+) during the starter, grower, and finisher phase. Performance, activity, behaviour, and body damage were recorded. LP and LP-E+ had a lower feed intake, growth, and gain-to-feed ratio, and were more active than NP and LP+ pigs. LP-E+ pigs interacted most often with enrichment materials, followed by LP, LP+, and NP pigs. LP pigs showed more tail biting than all other groups during the starter phase and the finisher phase (tendency) compared to NP and LP+ pigs. Thus, LP-E+ only reduced tail biting in the starter phase, whereas LP+ tended to do so throughout. Tail damage was more severe in LP pigs than in NP and LP+, with LP-E+ in between. In conclusion, IAA supplementation was more effective than extra environmental enrichment in countering the negative effects of a low protein diet on tail biting in pigs.

Evidence for the protein leverage hypothesis in preschool children prone to obesity

BACKGROUND & AIMS

The protein leverage hypothesis (PLH) proposed that strict regulation of protein intake drives energy overconsumption and obesity when diets are diluted by fat and/or carbohydrates. Evidence about the PLH has been found in adults, while studies in children are limited. Thus, we aimed to test the PLH by assessing the role of dietary protein on macronutrients, energy intake, and obesity risk using data from preschool children followed for 1.3 years.

METHODS

553 preschool children aged 2-6 years from the 'Healthy Start' project were included.

EXPOSURES

The proportion of energy intake from protein, fat, and carbohydrates collected from a 4-day dietary record.

OUTCOMES

Energy intake, BMI z-score, fat mass (FM) %, waist- (WHtR) and hip-height ratio (HHtR). Power function analysis was used to test the leverage of protein on energy intake. Mixture models were used to explore interactive associations of macronutrient composition on all these outcomes, with results visualized as response surfaces on the nutritional geometry.

RESULTS

Evidence for the PLH was confirmed in preschool children. The distribution of protein intake (% of MJ, IQR: 3.2) varied substantially less than for carbohydrate (IQR: 5.7) or fat (IQR: 6.3) intakes, suggesting protein intake is most tightly regulated. Absolute energy intake varied inversely with dietary percentage energy from protein (L = -0.14, 95% CI: -0.25, -0.04). Compared to children with high fat or carbohydrate intakes, children with high dietary protein intake (>20% of MJ) had a greater decrease in WHtR and HHtR over the 1.3-year follow-up, offering evidence for the PLH in prospective analysis. But no association was observed between macronutrient distribution and changes in BMI z-score or FM%.

CONCLUSIONS

In this study in preschool children, protein intake was the most tightly regulated macronutrient, and energy intake was an inverse function of dietary protein concentration, indicating the evidence for protein leverage. Increases in WHtR and HHtR were principally associated with the dietary protein dilution, supporting the PLH. These findings highlight the importance of protein in children's diets, which seems to have significant implications for childhood obesity risk and overall health.

Protein and amino acids in obesity: friends or foes?

PURPOSE OF REVIEW

Nutritional interventions using protein and amino acids in obesity are popular therapeutical strategies to limit obesity development. However, the effects of dietary protein intake and amino acid metabolic alterations involved in obesity pathophysiology have not been completely unravelled. Significant recent studies have brought to light new findings in these areas, which are the primary focus of this review.

RECENT FINDINGS

We describe the effects of protein intake on weight regain prevention, the influence on gut microbiota, the response to low-protein highly processed foods, and the contrasting impacts of a high-protein diet on adults and children. We also explore newly discovered correlations between amino acids, liver fat accumulation, and the dysregulation of the liver-pancreas axis due to alterations in amino acid levels in the context of obesity. Lastly, we consider branched-chain amino acids, along with glycine and tryptophan, as significant biomarkers during periods of positive or negative energy balance.

SUMMARY

Interventions using dietary protein in obesity may be useful, especially during energy restriction but also in sarcopenic obesity. Furthermore, metabolic profiles that encompass alterations in certain amino acids can provide valuable insights into the metabolic condition of patients with obesity, particularly in relation to insulin resistance and the risk of developing type 2 diabetes.

Diet composition and energy intake in humans

Absolute energy from fats and carbohydrates and the proportion of carbohydrates in the food supply have increased over 50 years. Dietary energy density (ED) is primarily decreased by the water and increased by the fat content of foods. Protein, carbohydrates and fat exert different effects on satiety or energy intake (EI) in the order protein > carbohydrates > fat. When the ED of different foods is equalized the differences between fat and carbohydrates are modest. Covertly increasing dietary ED with fat, carbohydrate or mixed macronutrients elevates EI, producing weight gain and vice versa. In more naturalistic situations where learning cues are intact, there appears to be greater compensation for the different ED of foods. There is considerable individual variability in response. Macronutrient-specific negative feedback models of EI regulation have limited capacity to explain how availability of cheap, highly palatable, readily assimilated, energy-dense foods lead to obesity in modern environments. Neuropsychological constructs including food reward (liking, wanting and learning), reactive and reflective decision making, in the context of asymmetric energy balance regulation, give more comprehensive explanations of how environmental superabundance of foods containing mixtures of readily assimilated fats and carbohydrates and caloric beverages elevate EI through combined hedonic, affective, cognitive and physiological mechanisms. This article is part of a discussion meeting issue 'Causes of obesity: theories, conjectures and evidence (Part II)'.

The provisioned primate: patterns of obesity across lemurs, monkeys, apes and humans

Non-human primates are potentially informative but underutilized species for investigating obesity. I examined patterns of obesity across the Primate order, calculating the ratio of body mass in captivity to that in the wild. This index, relative body mass, for n = 40 non-human primates (mean ± s.d.: females: 1.28 ± 0.30, range 0.67-1.78, males: 1.24 ± 0.28, range 0.70-1.97) overlapped with a reference value for humans (women: 1.52, men: 1.44). Among non-human primates, relative body mass was unrelated to dietary niche, and was marginally greater among female cohorts of terrestrial species. Males and females had similar relative body masses, but species with greater sexual size dimorphism (male/female mass) in wild populations had comparatively larger female body mass in captivity. Provisioned populations in wild and free-ranging settings had similar relative body mass to those in research facilities and zoos. Compared to the wild, captive diets are unlikely to be low in protein or fat, or high in carbohydrate, suggesting these macronutrients are not driving overeating in captive populations. Several primate species, including chimpanzees, a sister-species to humans, had relative body masses similar to humans. Humans are not unique in the propensity to overweight and obesity. This article is part of a discussion meeting issue 'Causes of obesity: theories, conjectures and evidence (Part II)'.

Protein appetite as an integrator in the obesity system: the protein leverage hypothesis

Despite the large volume and extensive range of obesity research, there is substantial disagreement on the causes and effective preventative strategies. We suggest the field will benefit from greater emphasis on integrative approaches that examine how various potential contributors interact, rather than regarding them as competing explanations. We demonstrate the application of nutritional geometry, a multi-nutrient integrative framework developed in the ecological sciences, to obesity research. Such studies have shown that humans, like many other species, regulate protein intake more strongly than other dietary components, and consequently if dietary protein is diluted there is a compensatory increase in food intake-a process called protein leverage. The protein leverage hypothesis (PLH) proposes that the dilution of protein in modern food supplies by fat and carbohydrate-rich highly processed foods has resulted in increased energy intake through protein leverage. We present evidence for the PLH from a variety of sources (mechanistic, experimental and observational), and show that this mechanism is compatible with many other findings and theories in obesity research. This article is part of a discussion meeting issue 'Causes of obesity: theories, conjectures and evidence (Part II)'.

From dearth to excess: the rise of obesity in an ultra-processed food system

More people now have obesity than suffer from starvation thanks to our modern food system. Agriculture was transformed over the 20th century by a variety of technological advancements that relied heavily on fossil fuels. In the United States, government policies and economic incentives led to surplus production of cheap inputs to processed food industries that produced a wide variety of heavily marketed, convenient, rewarding, timesaving, and relatively inexpensive ultra-processed foods. The energy available in the food supply increased by much more than the population needs, albeit with large inequities in nutrition security. While most of the rise in per capita food availability during the late 20th and early 21st centuries in the United States resulted in increased food waste, a variety of mechanisms have been proposed by which changes in the increasingly ultra-processed food environment resulted in excess energy intake disproportionately in people genetically susceptible to obesity. As populations continue to grow, substantial investments in coordinated nutrition and agricultural research are needed to transform our current food system to one that relies less on fossil fuels, preserves biodiversity, ensures environmental health, and provides equitable access to affordable, safe and nutritious food that reduces the prevalence of chronic diet-related diseases like obesity. This article is part of a discussion meeting issue 'Causes of obesity: theories, conjectures and evidence (Part I)'.

The fructose survival hypothesis for obesity

The fructose survival hypothesis proposes that obesity and metabolic disorders may have developed from over-stimulation of an evolutionary-based biologic response (survival switch) that aims to protect animals in advance of crisis. The response is characterized by hunger, thirst, foraging, weight gain, fat accumulation, insulin resistance, systemic inflammation and increased blood pressure. The process is initiated by the ingestion of fructose or by stimulating endogenous fructose production via the polyol pathway. Unlike other nutrients, fructose reduces the active energy (adenosine triphosphate) in the cell, while blocking its regeneration from fat stores. This is mediated by intracellular uric acid, mitochondrial oxidative stress, the inhibition of AMP kinase and stimulation of vasopressin. Mitochondrial oxidative phosphorylation is suppressed, and glycolysis stimulated. While this response is aimed to be modest and short-lived, the response in humans is exaggerated due to gain of 'thrifty genes' coupled with a western diet rich in foods that contain or generate fructose. We propose excessive fructose metabolism not only explains obesity but the epidemics of diabetes, hypertension, non-alcoholic fatty liver disease, obesity-associated cancers, vascular and Alzheimer's dementia, and even ageing. Moreover, the hypothesis unites current hypotheses on obesity. Reducing activation and/or blocking this pathway and stimulating mitochondrial regeneration may benefit health-span. This article is part of a discussion meeting issue 'Causes of obesity: theories, conjectures and evidence (Part I)'.

No strong evidence of the protein leverage hypothesis in pregnant women with obesity and their infants

OBJECTIVE

The goal of this study was to investigate the role of dietary protein on macronutrient and energy intake, maternal adiposity during pregnancy, and infant adiposity at birth.

METHODS

In 41 women with obesity, early-pregnancy (13-16 weeks) protein intake was assessed with food photography and expressed as a ratio of Estimated Average Requirements (EAR) in pregnancy for protein (0.88 g/kg/d), herein "protein balance." Energy intake was measured by the intake-balance method, gestational weight gain as grams per week, and fat mass by a three-compartment model. Spearman correlations and linear models were computed using R version 4.1.1 (p < 0.05 considered significant).

RESULTS

Women had a mean (SD) age of 27.5 (4.8) years and a pregravid BMI of 34.4 (2.9), kg/m2 , and the majority were non-White (n = 23, 56.1%). Protein balance in early pregnancy was not significantly associated with energy intake across mid and mid/late pregnancy (β = 328.7, p = 0.30 and β = 286.2, p = 0.26, respectively) or gestational weight gain (β = 117.0, p = 0.41). Protein balance was inversely associated with fat mass in early, mid, and late pregnancy (β = -10.6, p = 0.01, β = -10.4, p = 0.03, β = -10.3, p = 0.03, respectively). Protein balance did not predict infant adiposity at birth (p > 0.05).

CONCLUSIONS

Low protein intake may have been present before pregnancy, explaining early relationships with adiposity in this cohort. The protein leverage hypothesis is likely not implicated in the intergenerational transmission of obesity.

Determining the metabolic effects of dietary fat, sugars and fat-sugar interaction using nutritional geometry in a dietary challenge study with male mice

The metabolic effects of sugars and fat lie at the heart of the "carbohydrate vs fat" debate on the global obesity epidemic. Here, we use nutritional geometry to systematically investigate the interaction between dietary fat and the major monosaccharides, fructose and glucose, and their impact on body composition and metabolic health. Male mice (n = 245) are maintained on one of 18 isocaloric diets for 18-19 weeks and their metabolic status is assessed through in vivo procedures and by in vitro assays involving harvested tissue samples. We find that in the setting of low and medium dietary fat content, a 50:50 mixture of fructose and glucose (similar to high-fructose corn syrup) is more obesogenic and metabolically adverse than when either monosaccharide is consumed alone. With increasing dietary fat content, the effects of dietary sugar composition on metabolic status become less pronounced. Moreover, higher fat intake is more harmful for glucose tolerance and insulin sensitivity irrespective of the sugar mix consumed. The type of fat consumed (soy oil vs lard) does not modify these outcomes. Our work shows that both dietary fat and sugars can lead to adverse metabolic outcomes, depending on the dietary context. This study shows how the principles of the two seemingly conflicting models of obesity (the "energy balance model" and the "carbohydrate insulin model") can be valid, and it will help in progressing towards a unified model of obesity. The main limitations of this study include the use of male mice of a single strain, and not testing the metabolic effects of fructose intake via sugary drinks, which are strongly linked to human obesity.

Nutrigonometry IV: Thales' theorem to measure the rules of dietary compromise in animals

Diet specialists and generalists face a common challenge: they must regulate the intake and balance of nutrients to achieve a target diet for optimum nutrition. When optimum nutrition is unattainable, organisms must cope with dietary imbalances and trade-off surplus and deficits of nutrients that ensue. Animals achieve this through compensatory rules that dictate how to cope with nutrient imbalances, known as 'rules of compromise'. Understanding the patterns of the rules of compromise can provide invaluable insights into animal physiology and behaviour, and shed light into the evolution of diet specialisation. However, we lack an analytical method for quantitative comparisons of the rules of compromise within and between species. Here, I present a new analytical method that uses Thales' theorem as foundation, and that enables fast comparisons of the rules of compromise within and between species. I then apply the method on three landmark datasets to show how the method enables us to gain insights into how animals with different diet specialisation cope with nutrient imbalances. The method opens new avenues of research to understand how animals cope with nutrient imbalances in comparative nutrition.

Nutrient balancing in a fruit-specialist primate, the black-and-white ruffed lemur (Varecia variegata)

Animals' foraging behavior and dietary choices are, in part, driven by their ultimate function: to meet nutritional demands. However, depending on their degree of dietary specialization and the availability and distribution of food resources in their environment, species may utilize different nutritional strategies. With shifting plant phenology, increasing unpredictability of fruiting, and declining food quality in response to anthropogenic climate change, existing nutritional constraints may become exacerbated. Such changes are especially concerning for Madagascar's endemic fruit specialists given the nutrient-limitation of the island's landscapes. In this study, we examined the nutritional strategy of one such fruit-specialist primate, the black-and-white ruffed lemur (Varecia variegata), over a 12-month period (January to December 2018) in Ranomafana National Park, Madagascar. We hypothesized that Varecia would balance nonprotein energy (NPE) to protein (AP) at a high ratio similar to other frugivorous primates, and that they would prioritize protein intake given their high degree of frugivory. We found that Varecia balance NPE:AP at a ratio of 11:1, higher than in any other primate studied to date; however, diets shifted such that nutrient balancing varied seasonally (12.6:1 abundant-9.6:1 lean). Varecia meet NRC suggested recommendations of 5-8% of calories from protein, despite having a diet mostly comprising fruits. However, seasonal shifts in NPE intakes result in significant energy shortfalls during fruit-lean seasons. Flowers provide an important source of NPE during these periods, with flower consumption best predicting lipid intake, suggesting this species' ability to shift resource use. Nevertheless, achieving adequate and balanced nutrient intakes may become precarious in the face of increasing unpredictability in plant phenology and other environmental stochasticities resulting from climate change.

Evidence for protein leverage in a general population sample of children and adolescents

BACKGROUND/OBJECTIVES

The strong regulation of protein intake can lead to overconsumption of total energy on diets with a low proportion of energy from protein, a process referred to as protein leverage. The protein leverage hypothesis posits that protein leverage explains variation in energy intake and potentially obesity in ecological settings. Here, we tested for protein leverage and the protein leverage hypothesis in children and adolescents.

SUBJECTS/METHODS

A population sample of children, mean (SD) age 7.6 (0.4) years (n = 422), followed up at age 9.8 (0.4) years (n = 387) and at age 15.8 (0.4) years (n = 229), participating for the Physical Activity and Nutrition in Children (PANIC) study.

EXPOSURES

4-day food records-related proportional energy intake of proteins, fats, and carbohydrates.

OUTCOMES

energy intake, body mass index (BMI) z-score and dual-energy X-ray absorptiometry-related energy expenditure.

RESULTS

Proportional energy intake of proteins was inversely associated with energy intake following power functions at all 3 ages (mean [95%CI] strength of leverage of L = -0.36 [-0.47 to -0.25]; L = -0.26 [-0.37 to -0.15]; L = -0.25 [-0.38 to -0.13]; all P < 0.001). Mixture analysis indicated that variance in energy intake was associated primarily with the proportional intake of energy from proteins, not with either fats or carbohydrates. At all 3 ages, energy intake was not associated with BMI z-score but positively associated with energy expenditure (all P < 0.001).

CONCLUSIONS

This study provides evidence consistent with protein leverage in a population sample of children and adolescents. Increased energy intake on diets with lower protein content was counterbalanced by increased energy expenditure and therefore did not translate into increased adiposity.

Macronutrient (im)balance drives energy intake in an obesogenic food environment: An ecological analysis

OBJECTIVE

The protein leverage hypothesis (PLH) postulates that strong regulation of protein intake drives energy overconsumption and obesity when human diets are diluted by fat and carbohydrates. The two predictions of the PLH are that humans (i) regulate intake to maintain protein within a narrow range and that (ii) energy intake is an inverse function of percentage energy from protein because absolute protein intake is maintained within narrow limits.

METHODS

Multidimensional nutritional geometry was used to test the predictions of the PLH using dietary data from the Australian National Nutrition and Physical Activity Survey.

RESULTS

Both predictions of the PLH were confirmed in a population setting: the mean protein intake was 18.4%, and energy intake decreased with increasing energy from protein (L = -0.18, p &lt; 0.0001). It was demonstrated that highly processed discretionary foods are a significant diluent of protein and associated with increased energy but not increased protein intake.

CONCLUSIONS

These results support an integrated ecological and mechanistic explanation for obesity, in which low-protein highly processed foods lead to higher energy intake because of the biological response to macronutrient imbalance driven by a dominant appetite for protein. This study supports a central role for protein in the obesity epidemic, with significant implications for global health.

Nutrigonometry III: curvature, area and differences between performance landscapes

Nutrition is one of the underlying factors necessary for the expression of life-histories and fitness across the tree of life. In recent decades, the geometric framework (GF) has become a powerful framework to obtain biological insights through the construction of multidimensional performance landscapes. However, to date, many properties of these multidimensional landscapes have remained inaccessible due to our lack of mathematical and statistical frameworks for GF analysis. This has limited our ability to understand, describe and estimate parameters which may contain useful biological information from GF multidimensional performance landscapes. Here, we propose a new model to investigate the curvature of GF multidimensional landscapes by calculating the parameters from differential geometry known as Gaussian and mean curvatures. We also estimate the surface area of multidimensional performance landscapes as a way to measure landscape deviations from flat. We applied the models to a landmark dataset in the field, where we also validate the assumptions required for the calculations of curvature. In particular, we showed that linear models perform as well as other models used in GF data, enabling landscapes to be approximated by quadratic polynomials. We then introduced the Hausdorff distance as a metric to compare the similarity of multidimensional landscapes.

Generational issues in linking family farming production, traditional food in diet, physical activity and obesity in Pacific Islands countries and territories: the case of the Melanesian population on Lifou Island

In the Melanesian culture, traditional activities are organized around family farming, although the lifestyle transition taking place over the last several decades has led to imbalances in diet and physical activity, with both leading to obesity. The aim of this interdisciplinary study was to understand the links between family farming (produced, exchanged, sold, and consumed food), diet (focused on produced, hunted, and caught food), physical activity (sedentary, light, and moderate-to-vigorous physical activity) and obesity in Melanesian Lifou Island families (parents and children). Forty families, including 142 adults and children, completed individual food frequency questionnaires, wore tri-axial accelerometers for seven continuous days, and had weight and height measured with a bio-impedance device. A family farming questionnaire was conducted at the household level concerning family farming practices and sociodemographic variables. Multinomial regression analyses and logistic regression models were used to analyze the data. Results showed that family farming production brings a modest contribution to diet and active lifestyles for the family farmers of Lifou Island. The drivers for obesity in these tribal communities were linked to diet in the adults, whereas parental socioeconomic status and moderate-to-vigorous physical activity were the main factors associated to being overweight and obesity in children. These differences in lifestyle behaviors within families suggest a transition in cultural practices at the intergenerational level. Future directions should consider seasonality and a more in-depth analysis of diet including macro- and micro- nutrients to acquire more accurate information on the intergenerational transition in cultural practices and its consequences on health outcomes in the Pacific region.

A Comparison of the Australian Dietary Guidelines to the NOVA Classification System in Classifying Foods to Predict Energy Intakes and Body Mass Index

NOVA classification distinguishes foods by level of processing, with evidence suggesting that a high intake of ultra-processed foods (UPFs, NOVA category 4) leads to obesity. The Australian Dietary Guidelines, in contrast, discourage excess consumption of “discretionary foods” (DFs), defined according to their composition. Here, we (i) compare the classification of Australian foods under the two systems, (ii) evaluate their performance in predicting energy intakes and body mass index (BMI) in free-living Australians, and (iii) relate these outcomes to the protein leverage hypothesis of obesity. Secondary analysis of the Australian National Nutrition and Physical Activity Survey was conducted. Non-protein energy intake increased by 2.1 MJ (p < 0.001) between lowest and highest tertiles of DF intake, which was significantly higher than UPF (0.6 MJ, p < 0.001). This demonstrates that, for Australia, the DF classification better distinguishes foods associated with high energy intakes than does the NOVA system. BMI was positively associated with both DFs (−1. 0, p = 0.0001) and UPFs (−1.1, p = 0.0001) consumption, with no difference in strength of association. For both classifications, macronutrient and energy intakes conformed closely to the predictions of protein leverage. We account for the similarities and differences in performance of the two systems in an analysis of Australian foods.

The limitations of investigating appetite through circuit manipulations: are we biting off more than we can chew?

Disordered eating can underpin a number of debilitating and prevalent chronic diseases, such as obesity. Broader advances in psychopharmacology and biology have motivated some neuroscientists to address diet-induced obesity through reductionist, pre-clinical eating investigations on the rodent brain. Specifically, chemogenetic and optogenetic methods developed in the 21st century allow neuroscientists to perform in vivo, region-specific/projection-specific/promoter-specific circuit manipulations and immediately assess the impact of these manipulations on rodent feeding. These studies are able to rigorously conclude whether a specific neuronal population regulates feeding behaviour in the hope of eventually developing a mechanistic neuroanatomical map of appetite regulation. However, an artificially stimulated/inhibited rodent neuronal population that changes feeding behaviour does not necessarily represent a pharmacological target for treating eating disorders in humans. Chemogenetic/optogenetic findings must therefore be triangulated with the array of theories that contribute to our understanding of appetite. The objective of this review is to provide a wide-ranging discussion of the limitations of chemogenetic/optogenetic circuit manipulation experiments in rodents that are used to investigate appetite. Stepping into and outside of medical science epistemologies, this paper draws on philosophy of science, nutrition, addiction biology and neurophilosophy to prompt more integrative, transdisciplinary interpretations of chemogenetic/optogenetic appetite data. Through discussing the various technical and epistemological limitations of these data, we provide both an overview of chemogenetics and optogenetics accessible to non-neuroscientist obesity researchers, as well as a resource for neuroscientists to expand the number of lenses through which they interpret their circuit manipulation findings.

Testing the protein-leverage hypothesis using population surveillance data

It is hypothesized that humans exhibit 'protein leverage' (PL), whereby regulation of absolute protein intake results in the over-consumption of non-protein food on low percentage protein diets. Testing for PL using dietary surveillance data involves seeking evidence for a negative association between total energy intake and percentage energy from protein. However, it is unclear whether such an association might emerge without PL due to the structure of intake data (protein and non-protein intakes have different means and variances and covary). We derive a set of models that describe the association between the expected estimate of PL and the distributions of protein and non-protein intake. Models were validated via simulation. Patterns consistent with PL will not emerge simply because protein intake has a lower mean and/or variance than non-protein. Rather, evidence of PL is observed where protein has a lower index of dispersion (variance/mean) than non-protein intake. Reciprocally, the stronger PL is the lower the index of dispersion for protein intake becomes. Disentangling causality is ultimately beyond the power of observational data alone. However, we show that one can correct for confounders (e.g. age) in generating signals of PL, and describe independent measures that can anchor inferences around the role of PL.

Stone tools improve diet quality in wild monkeys

Tool use is a fundamental feature of human evolution. Stone tools are in the archaeological record from 3.4 Ma, even before Homo,¹ and the use of stone tools probably predated the split between hominins and panins.² Using tools (hereafter, tooling cf Fragaszy and Mangalam³) is hypothesized to have improved hominins' foraging efficiency or access to high-quality foods.^4-7 This hypothesis is supported if feeding with tools positively contributes to diet quality in extant non-human primates or if foraging efficiency is increased by tooling. However, the contribution of tooling to non-human primates' foraging success has never been investigated through a direct analysis of nutritional ecology.^8,9 We used multi-dimensional nutritional geometry to analyze energy and macronutrients (nonstructural carbohydrates, lipids, and protein) in the diets of wild capuchin monkeys (Sapajus libidinous) that routinely crack palm nuts with stone hammers.^10,11 We show that eating nuts obtained through tooling helps monkeys to achieve more consistent dietary intakes. Tooling increased the net energy gain by 50% and decreased the proportion of fiber ingested by 7%. Tooling also increased the daily non-protein energy intake. By contrast, protein intake remained constant across foraging days, suggesting a pattern of macronutrient regulation called protein prioritization, which is also found in contemporary humans.^8,9 In addition, tooling reduced dispersion in the ratio of protein to non-protein energy, suggesting a role in macronutrient balancing. Our findings suggest that tooling prior to tool making could have substantially increased the nutritional security of ancestral hominins, sowing the seeds for cultural development.^5,7 VIDEO ABSTRACT.

The health effects of soy: A reference guide for health professionals

Soy is a hotly debated and widely discussed topic in the field of nutrition. However, health practitioners may be ill-equipped to counsel clients and patients about the use of soyfoods because of the enormous, and often contradictory, amount of research that has been published over the past 30 years. As interest in plant-based diets increases, there will be increased pressure for practitioners to gain a working knowledge of this area. The purpose of this review is to provide concise literature summaries (400-500 words) along with a short perspective on the current state of knowledge of a wide range of topics related to soy, from the cholesterol-lowering effects of soy protein to the impact of isoflavones on breast cancer risk. In addition to the literature summaries, general background information on soyfoods, soy protein, and isoflavones is provided. This analysis can serve as a tool for health professionals to be used when discussing soyfoods with their clients and patients.

Restriction of dietary protein in rats increases progressive-ratio motivation for protein

Low-protein diets can impact food intake and appetite, but it is not known if motivation for food is changed. In the present study, we used an operant behavioral task - the progressive ratio test - to assess whether motivation for different foods was affected when rats were maintained on a protein-restricted diet (REST, 5% protein diet) compared to non-restricted control rats (CON, 18% protein). Rats were tested either with nutritionally-balanced pellets (18.7% protein, Experiment 1) or protein-rich pellets (35% protein, Experiment 2) as reinforcers. Protein restriction increased breakpoint for protein-rich pellets, relative to CON rats, whereas no difference in breakpoint for nutritionally-balanced pellets was observed between groups. When given free access to either nutritionally-balanced pellets or protein-rich pellets, REST and CON rats did not differ in their intake. We also tested whether a previous history of protein restriction might affect present motivation for different types of food by assessing breakpoint of previously REST animals that were subsequently put on standard maintenance chow (protein-repleted rats, REPL, Experiment 2). REPL rats did not show increased breakpoint, relative to their initial encounter with protein-rich pellets while they were protein-restricted. This study demonstrates that restriction of dietary protein induces a selective increased motivation for protein-rich food, a behavior that disappears once rats are not in need of protein.

Intermittent fasting two days versus one day per week, matched for total energy intake and expenditure, increases weight loss in overweight/obese men and women

Background

Intermittent fasting (IF), consisting of either a one-day (IF1) or two consecutive days (IF2) per week, is commonly used for optimal body weight loss. Our laboratory has previously shown an IF1 diet combined with 6d/week of protein pacing (P; 4–5 meals/day evenly spaced, ~ 30% protein/day) significantly enhances weight loss, body composition, and cardiometabolic health in obese men and women. Whether an IF1-P or IF2-P, matched for weekly energy intake (EI) and expenditure (EE), is superior for weight loss, body composition, and cardiometabolic health is unknown.

Methods

This randomized control study directly compared an IF1-P (n = 10) versus an IF2-P (n = 10) diet on weight loss and body composition, cardiovascular (blood pressure and lipids), hormone, and hunger responses in 20 overweight men and women during a 4-week weight loss period. Participants received weekly dietary counseling and monitoring of compliance from a registered dietitian. All outcome variables were assessed pre (week 0) and post (week 5).

Results

Both groups significantly reduced body weight, waist circumference, percent body fat, fat mass, hunger, blood pressure, lipids, glucose, and increased percent fat-free mass (p < 0.05). However, IF2-P resulted in significantly greater reductions in body weight (-29%) and waist circumference (-38%) compared to IF1-P (p < 0.05), and showed a strong tendency for greater reductions in fat mass, glucose, and hunger levels (p < 0.10) despite similar weekly total EI (IF1-P, 9058 ± 692 vs. IF2-P, 8389 ± 438 kcals/week; p = 0.90), EE (~ 300 kcals/day; p = 0.79), and hormone responses (p > 0.10).

Conclusions

These findings support short-term IF1-P and IF2-P to optimize weight loss and improve body composition, cardiometabolic health, and hunger management, with IF2-P providing enhanced benefits in overweight women and men.

Trial registration

This trial was registered March 03, 2020 at www.clinicaltrials.gov as NCT04327141.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12937-022-00790-0.

Perspective: Soybeans Can Help Address the Caloric and Protein Needs of a Growing Global Population

Feeding a growing global population with projected rising socioeconomic status will require additional sources of calories and especially protein. These sources need to align with the Sustainable Development Goals established by the Food and Agriculture Organization of the United Nations. The soybean is uniquely positioned to meet this challenge based on the following criteria: (1) Global soybean production exceeds by ~4 times the production of all pulses combined (2) Soybeans are higher in protein than other legumes and soy protein quality is similar to animal protein quality (3) Soybeans are an excellent source of healthy fat, including both essential fatty acids (4) Soybeans, like other legumes, symbiotically fix atmospheric nitrogen thereby reducing the need for fertilizer inputs (5) Greenhouse gas emissions per unit protein are lower than for nearly all other foods (6) Soybeans, like other legumes, are also recognized as an affordable food that can be incorporated into diverse diets regardless of economic standing and (7) The range of foods produced from soybeans constitutes an important position in historic and contemporary cuisines, cultures and emerging consumer trends for plant-based protein. Although most soybeans are currently used for animal feed, soybean use is dictated by consumer demand. Therefore, soybeans are well positioned to meet future global needs for energy and protein. Armed with this knowledge, health professionals can feel justified in encouraging greater consumption of soyfoods for both personal and planetary reasons.

An integrative approach to dietary balance across the life course

Animals require specific blends of nutrients that vary across the life course and with circumstances, e.g., health and activity levels. Underpinning and complicating these requirements is that individual traits may be optimized on different dietary compositions leading to nutrition-mediated trade-offs among outcomes. Additionally, the food environment may constrain which nutrient mixtures are achievable. Natural selection has equipped animals for solving such multi-dimensional, dynamic challenges of nutrition, but little is understood about the details and their theoretical and practical implications. We present an integrative framework, nutritional geometry, which models complex nutritional interactions in the context of multiple nutrients and across levels of biological organization (e.g., cellular, individual, and population) and levels of analysis (e.g., mechanistic, developmental, ecological, and evolutionary). The framework is generalizable across different situations and taxa. We illustrate this using examples spanning insects to primates and settings (laboratory, and the wild), and demonstrate its relevance for human health.

Nutrient-sensitive approach for sustainability assessment of different dietary patterns in Australia

BACKGROUND

Understanding the relation between sustainability and nutrients is important in devising healthy and sustainable diets. However, there are no prevailing methodologies to assess sustainability at the nutrient level.

OBJECTIVES

The aim was to examine and demonstrate the potential of integrating input-output analysis with nutritional geometry to link environmental, economic, and health associations of dietary scenarios in Australia with macronutrients.

METHODS

One-day dietary recalls of 9341 adult respondents (age ≥18 y) of the latest available cross-sectional National Nutrition and Physical Activity Survey-2011/12 of Australia were integrated with the input-output data obtained from the Australian Industrial Ecology Virtual Laboratory to calculate the environmental and economic impacts of dietary intakes in Australia. Australian adults' dietary intakes were classified into 3 dietary scenarios: "vegan," "pescatarian," and "omnivorous." Then, the relations between nutritional, economic, and environmental characteristics of the 3 dietary scenarios were demonstrated with the diets' macronutrient composition in a multidimensional nutritional geometry representation to link the sustainability indicators with macronutrients.

RESULTS

Nutrient density and economic and environmental indicators increased as the percentage of energy from proteins increased and decreased as the percentage of energy from fats increased for the 3 dietary scenarios, except for the nutrient density and water use of the "vegan" dietary scenario. Energy density increased as the percentage of energy from fats increased and decreased as the percentage of energy from proteins increased for "pescatarian" and "omnivorous" dietary scenarios. In the "vegan" dietary scenario, nutrient density and water use increased as the percentage of energy from proteins increased; however, these decreased as the percentage of energy from carbohydrates increased, instead of fats.

CONCLUSIONS

The study presents a new approach to analyzing the relations between sustainability indicators, foods, and macronutrients and establishes that proteins, irrespective of the source of protein, are driving dietary environmental and economic impacts.

Starter feed for carnivorous species as a practical replacement of bloodworms for a vertebrate model organism in ageing, the turquoise killifish Nothobranchius furzeri

The absence of a controlled diet is unfortunate in a promising model organism for ageing, the turquoise killifish (Nothobranchius furzeri Jubb, 1971). Currently captive N. furzeri are fed bloodworms but it is not known whether this is an optimal diet. Replacing bloodworms with a practical dry feed would reduce diet variability. In the present study, we estimated the nutritional value of the diet ingested by wild fish and determined the fish-body amino acid profile as a proxy for their nutritional requirements. We compared the performance of fish fed four commercial feeds containing 46%-64% protein to that achieved with bloodworms and that of wild fish. Wild fish target a high-protein (60%) diet and this is supported by their superior performance on high-protein diets in captivity. In contrast, feeds for omnivores led to slower growth, lower fecundity and unnatural liver size. In comparison to wild fish, a bloodworm diet led to lower body condition, overfeeding and male liver enlargement. Out of the four dry feeds tested, the fish fed Aller matched wild fish in body condition and liver size, and was comparable to bloodworms in terms of growth and fecundity. A starter feed for carnivorous species appears to be a practical replacement for bloodworms for N. furzeri. The use of dry feeds improved performance in comparison to bloodworms and thus may contribute to reducing response variability and improving research reproducibility in N. furzeri research.

Obesogenic diets induce anxiety in rodents: A systematic review and meta-analysis

Obesity and mood disorders have been linked in a positive feedback loop. However, due to the bidirectional relationship between obesity and mental health, it is not clear whether anxiety is correlated with or caused by consumption of obesogenic diets. Here, we present a meta-analysis on the effects of dietary manipulation on rodent behavior in the elevated plus maze and open field test, the most common tests of anxiety-like behavior in animal models. The main dataset examined effects of obesogenic diets on time spent in the open and movement around the mazes. Auxiliary datasets examined effects of caloric restriction and protein restriction. Obesogenic diets had a negative effect on the time spent in the open overall. Effects were stronger in males than females. No effect of diet on locomotion was found, indicating that increases in anxiety-like behavior are not due to altered activity levels. No consistent effect of caloric restriction was observed, whereas protein restriction was associated with an increase in the time spent in the open. We show that obesogenic diets have a causative effect on anxiety-like behaviors in rodents, and not via a change in activity. Further studies are required to determine why obesogenic diets induce these behavioral changes.

Food Reward after Bariatric Surgery and Weight Loss Outcomes: An Exploratory Study

Changes in food preferences after bariatric surgery may alter its effectiveness as a treatment for obesity. We aimed to compare food reward for a comprehensive variety of food categories between patients who received a sleeve gastrectomy (SG) or a Roux-en-Y gastric bypass (RYGB) and to explore whether food reward differs according to weight loss. In this cross-sectional exploratory study, food reward was assessed using the Leeds Food Preference Questionnaire (LFPQ) in patients at 6, 12, or 24 months after SG or RYGB. We assessed the liking and wanting of 11 food categories. Comparisons were done regarding the type of surgery and total weight loss (TWL; based on tertile distribution). Fifty-six patients (30 SG and 26 RYGB) were included (women: 70%; age: 44.0 (11.1) y). Regarding the type of surgery, scores were not significantly different between SG and RYGB, except for ‘non-dairy products—without color’ explicit liking (p = 0.04). Regarding TWL outcomes, explicit liking, explicit wanting, and implicit wanting, scores were significantly higher for good responders than low responders for ‘No meat—High fat’ (post-hoc corrected p-value: 0.04, 0.03, and 0.04, respectively). Together, our results failed to identify major differences in liking and wanting between the types of surgery and tended to indicate that higher weight loss might be related to a higher reward for high protein-content food. Rather focus only on palatable foods, future studies should also consider a broader range of food items, including protein reward.