Diet composition and energy intake in humans

Research on the Optimization of Dietary Energy Supply in Growing and Fattening Pigs Under a Low-Temperature Environment

The purpose of this study was to investigate the effects of the optimization of dietary energy supply on the growth performance, nutrient digestibility, energy metabolism, nutrient oxidation, slaughter performance, and meat quality of growing and fattening pigs under a low-temperature environment. In this study, forty-eight 60-day-old growing barrows (Duroc × Landrace × Large White) with an initial body weight of 31.24 ± 3.56 kg were completely randomized into two treatment groups, with four replicates in each treatment group and six pigs in each replicate. The two groups were fed diets with equal protein levels and different energy levels (a conventional diet and an energy-optimized diet); the dietary energy level was increased by 8% by adding 6% fat, and the two groups were kept at the same ambient temperature (10 ± 1 °C) all day. After 5 d of prefeeding, the final weight reached approximately 110.00 kg prior to slaughter (99 days of age), and four pigs with a body weight of about 80.00 kg were selected in the two groups for digestion, metabolism, and respiratory calorimetry. The results showed that the average daily feed intake of the TES group (energy-optimized diet group, high fat and energy) was lower than that of the CON group (conventional diet group, normal fat and energy) (p < 0.05). Compared with the CON group, the feed-to-gain ratio was lower in the TES group during the fattening period (60-110 kg) (p < 0.05). Compared to the CON group, fat and energy digestibility in the TES group were higher (p < 0.05), fecal nitrogen and urine nitrogen were lower (p < 0.05), the nitrogen deposition rate increased (p < 0.05), and fat oxidation and the sedimentation energy rate also increased (p < 0.05). The serum triglyceride concentration in the TES group was higher than that in the CON group (p < 0.05). Compared to the CON group, the carcass weight, body fat content, backfat thickness, and eye muscle area in the TES group increased (p < 0.05); the L* value of flesh color also increased (p < 0.05); and the shear force was lower (p < 0.05). The dietary energy should be optimized under a low-temperature environment, and the feed conversion efficiency of fattening pigs could be improved by improving dietary energy levels by adding fat, increasing the fat oxidation proportion, promoting nitrogen deposition and sedimentation energy, and improving slaughter performance and meat quality.

Energy and Macronutrient Dietary Intakes of Vegetarian and Semi-Vegetarian Serbian Adults: Data from the EFSA EU Menu Food Consumption Survey (2017-2022)

This study is the first to examine the diet and nutritional status of the adult vegetarian and semi-vegetarian population in Serbia, using data from the EFSA EU Menu Food Consumption Survey 2017-2022. The survey included 314 participants (63 vegans, 192 lacto-ovo vegetarians, 50 pescatarians, and 9 flexitarians), aged 18-74 years (166 women and 148 men, with no gender differences in dietary patterns) across all regions of Serbia. Collected data included anthropometrics (BMI) and intake of energy, macronutrients, and specific food groups (assessed through two 24 h dietary recalls). The study revealed multiple nutritional shortcomings across all three dietary patterns. The most significant was an insufficient protein intake (especially among vegans, but also among non-vegans), connected with an unsatisfactory protein quantity, quality, and availability in plant sources. There was also a high fat intake (particularly from omega-6 and trans-fats-rich sources), especially among non-vegans (but also among vegans), while the intake of omega-3 sources was low. Non-vegans consumed less carbohydrates, fiber, vegetables, and fruit, but more sweets, beverages, and alcohol. Our findings highlight the need for improved nutritional education of vegetarians/semi-vegetarians in Serbia and the development of national food system-based guidelines for this population.

Involvement of mitochondrial dysfunction and oxidative stress in the nephrotoxicity induced by high-fat diet in Sprague-Dawley rats

The prevalence of obesity-associated kidney injury has increased, yet the precise extent of the injury and its underlying mechanisms remain unclear. This study used a Sprague-Dawley (SD) rat model to simulate human exposure scenarios, with the objective of investigating the involvement of mitochondria in obesity-induced renal toxicity. Biochemical analysis revealed significant increases in serum creatinine, cystatin C, urinary protein, urinary microalbumin, and urinary α1-microglobulin levels in rats fed a high-fat diet, indicating a notable decline in glomerular filtration function. Histopathological examination showed mild to moderate degeneration in renal tubular epithelial cells, slight glomerular enlargement, fusion and disappearance of pedunculated cell, and decreased electron density of mitochondrial matrix and cristae, indicating the impaired filtration function of kidney. Furthermore, the study found reduced mitochondrial membrane potential and superoxide dismutase (SOD) levels, along with increased malondialdehyde (MDA) levels, signifying elevated mitochondrial oxidative stress in the kidneys of high-fat diet-fed rats. Additionally, a decrease in the number of mitochondrial uncoupling protein-2 (UCP-2) and proliferator-activated receptor gamma coactivator 1-alpha (PGC1α)-positive cells, as well as reduced protein expression levels in the mitochondria, suggests a reduced renal mitochondrial resistance to oxidative stress. Collectively, these findings indicate that a high-fat diet triggers abnormalities in both renal filtration and structural functionality in SD rats. The observed reduction in renal mitochondrial density and the elevation in oxidative stress levels could potentially serve as underlying mechanisms.

Lifestyle Therapy for Obesity

Lifestyle management of obesity includes nutritional therapy, physical activity, and several intermittent fasting therapies. Effective nutrition therapies include optimized low-fat diets, high-quality ketogenic diets, and energy-restricted diets. Adherence to dietary change remains the most substantial barrier to success; therefore, patients engaging in lifestyle changes require intensive support and resources. Physical activity is shown to have benefits to body composition and disease risk beyond the effects on weight loss. Patients should be guided toward a regimen that is appropriate for their capacity for movement. Multiple intermittent fasting strategies have now been shown to cause substantial weight loss and metabolic health improvement.

Are all sugars equal? Role of the food source in physiological responses to sugars with an emphasis on fruit and fruit juice

High (free) sugar intakes can increase self-reported energy intake and are associated with unfavourable cardiometabolic health. However, sugar source may modulate the effects of sugars due to several mechanisms including the food matrix. The aim of this review was to assess the current state of evidence in relation to food source effects on the physiological responses to dietary sugars in humans relevant to cardiometabolic health. An additional aim was to review potential mechanisms by which food sources may influence such responses. Evidence from meta-analyses of controlled intervention trials was used to establish the balance of evidence relating to the addition of sugars to the diet from sugar-sweetened beverages, fruit juice, honey and whole fruit on cardiometabolic outcomes. Subsequently, studies which have directly compared whole fruit with fruit juices, or variants of fruit juices, were discussed. In summary, the sources of sugars can impact physiological responses, with differences in glycaemic control, blood pressure, inflammation, and acute appetite. Longer-term effects and mechanisms require further work, but initial evidence implicates physical structure, energy density, fibre, potassium and polyphenol content, as explanations for some of the observed responses.

Impaired metabolic flexibility to fasting is associated with increased ad libitum energy intake in healthy adults

OBJECTIVE

We investigated how changes in 24-h respiratory exchange ratio (RER) and substrate oxidation during fasting versus an energy balance condition influence subsequent ad libitum food intake.

METHODS

Forty-four healthy, weight-stable volunteers (30 male and 14 female; mean [SD], age 39.3 [11.0] years; BMI 31.7 [8.3] kg/m2) underwent 24-h energy expenditure measurements in a respiratory chamber during energy balance (50% carbohydrate, 30% fat, and 20% protein) and 24-h fasting. Immediately after each chamber stay, participants were allowed 24-h ad libitum food intake from computerized vending machines.

RESULTS

Twenty-four-hour RER decreased by 9.4% (95% CI: -10.4% to -8.5%; p < 0.0001) during fasting compared to energy balance, reflecting a decrease in carbohydrate oxidation (mean [SD], -2.6 [0.8] MJ/day; p < 0.0001) and an increase in lipid oxidation (2.3 [0.9] MJ/day; p < 0.0001). Changes in 24-h RER and carbohydrate oxidation in response to fasting were correlated with the subsequent energy intake such that smaller decreases in fasting 24-h RER and carbohydrate oxidation, but not lipid oxidation, were associated with greater energy intake after fasting (r = 0.31, p = 0.04; r = 0.40, p = 0.007; and r = -0.27, p = 0.07, respectively).

CONCLUSIONS

Impaired metabolic flexibility to fasting, reflected by an inability to transition away from carbohydrate oxidation, is linked with increased energy intake.

Cafeteria Diet Can Affect Bone Microarchitecture in Sedentary and Trained Male Rats

INTRODUCTION

Poor eating habits and a sedentary lifestyle can impair health. Regular physical activity improves the quality of life and is essential for bone health. Therefore, the present study aimed to evaluate the effects of the cafeteria diet on bone quality of sedentary and exercised rats.

METHODS

Sixty young male Wistar rats were divided into six groups (n=10) according to diet composition and activity level, being: SD+CON, standard diet and control; SD+SED, standard diet and sedentary; SD+EX, standard diet and exercised; CD+CON, cafeteria diet and control; CD+SED, cafeteria diet and sedentary; CD+EX, cafeteria diet and exercised. The exercise protocol consisted of 10 ladder-climbing sessions/day, 5 days/week, and the sedentary rats were maintained in individual cages with limited mobility. Body mass and food intake were evaluated weekly. After 10 weeks, the animals were euthanized, and white adipose tissue was collected. The bone structure was evaluated by densitometry, mechanical tests, histomorphometric, and micro-computed tomography analyses.

RESULTS

The cafeteria diet increased adipose tissue (p<0.001), decreased bone mineral density (p=0.004), and impaired biomechanical properties (p<0.05) and histomorphometry parameters (p=0.044). The sedentarism decreased bone mineral density (p<0.001) and biomechanical properties (p<0.05), and the exercise did not improve bone properties.

CONCLUSION

In this experimental model, it was concluded that the cafeteria diet and a sedentary lifestyle negatively affect bone, and ladder-climbing exercise could not prevent the effects of the unhealthy diet.

Investigating the Influence of Heavy Metals and Environmental Factors on Metabolic Syndrome Risk Based on Nutrient Intake: Machine Learning Analysis of Data from the Eighth Korea National Health and Nutrition Examination Survey (KNHANES)

This study delves into the complex interrelations among nutrient intake, environmental exposures (particularly to heavy metals), and metabolic syndrome. Utilizing data from the Korea National Health and Nutrition Examination Survey (KNHANES), machine learning techniques were applied to analyze associations in a cohort of 5719 participants, categorized into four distinct nutrient intake phenotypes. Our findings reveal that different nutrient intake patterns are associated with varying levels of heavy metal exposure and metabolic health outcomes. Key findings include significant variations in metal levels (Pb, Hg, Cd, Ni) across the clusters, with certain clusters showing heightened levels of specific metals. These variations were associated with distinct metabolic health profiles, including differences in obesity, diabetes prevalence, hypertension, and cholesterol levels. Notably, Cluster 3, characterized by high-energy and nutrient-rich diets, showed the highest levels of Pb and Hg exposure and had the most concerning metabolic health indicators. Moreover, the study highlights the significant impact of lifestyle habits, such as smoking and eating out, on nutrient intake phenotypes and associated health risks. Physical activity emerged as a critical factor, with its absence linked to imbalanced nutrient intake in certain clusters. In conclusion, our research underscores the intricate connections among diet, environmental factors, and metabolic health. The findings emphasize the need for tailored health interventions and policies that consider these complex interplays, potentially informing future strategies to combat metabolic syndrome and related health issues.

Breaking down silos: the multifaceted nature of obesity and the future of weight management

The continued global increase in the prevalence of obesity prompted a meeting at the Royal Society of London investigating causal mechanisms of the disease, 'Causes of obesity: theories, conjectures, and evidence' in October 2022. Evidence presented indicates areas of obesity science where there have been advancements, including an increased understanding of biological and physiological processes of weight gain and maintenance, yet it is clear there is still debate on the relative contribution of plausible causes of the modern obesity epidemic. Consensus was reached that obesity is not a reflection of diminished willpower, but rather the confluence of multiple, complex factors. As such, addressing obesity requires multifactorial prevention and treatment strategies. The accumulated evidence suggests that a continued focus primarily on individual-level contributors will be suboptimal in promoting weight management at the population level. Here, we consider individual biological and physiological processes within the broader context of sociodemographic and sociocultural exposures as well as environmental changes to optimize research priorities and public health efforts. This requires a consideration of a systems-level approach that efficiently addresses both systemic and group-specific environmental determinants, including psychosocial factors, that often serve as a barrier to otherwise efficacious prevention and treatment options. This article is part of a discussion meeting issue 'Causes of obesity: theories, conjectures and evidence (Part I)'.