The link between the gut microbiome and obesity is not well defined. Understanding of the role of the gut microbiome in weight and health management may lead to future revolutionary changes for treating obesity. This review examined the relationship between obesity and the gut microbiome, and the role of probiotics, prebiotics, and synbiotics for preventing and treating obesity. We used PubMed and Google Scholar to collect appropriate articles for the review. We showed that the gut microbiome has an impact on nutrient metabolism and energy expenditure. Moreover, different modalities of obesity treatment have been shown to change the diversity and composition of the gut microbiome; this raises questions about the role these changes may play in weight loss. In addition, studies have shown that supplementation with probiotics, prebiotics, and synbiotics may alter the secretion of hormones, neurotransmitters, and inflammatory factors, thus preventing food intake triggers that lead to weight gain. Further clinical studies are needed to better understand how different species of bacteria in the gut microbiome may affect weight gain, and to determine the most appropriate doses, compositions, and regimens of probiotics, prebiotics, and synbiotics supplementation for long-term weight control.

Intermittent fasting (IF) diets have recently gained popularity as a weight loss and antiaging method that attracts celebrity endorsements and public interest. Despite the growing use of IF, the debate over its safety and efficacy is still ongoing. Defined IF regimens include 5 different types: alternate-day fasting, periodic fasting, time-restricted feeding, less clearly defined IF (fast mimicking diet, juice fasting), and religious fasts. Our literature review highlights the effect of IF essentially on body weight and cardiometabolic risk factors. Intermittent fasting may be effective for weight loss and may improve cardiovascular and metabolic health, although the long-term sustainability of these effects has not been studied. While data on the safety of IF are sparse, the most frequent adverse effects (hunger, irritability, and impaired cognition) may dissipate within a month of the fasting period. Intermittent fasting is not recommended for pregnant or lactating women, children or adolescents during maturation, the elderly or underweight people, and individuals vulnerable to eating disorders.

The sex ratio at birth (SRB) is the ratio of male-to-female births. This ratio is slightly skewed toward males (about 105 males to 100 females). However, several studies mostly in experimental animals have raised the question of whether the sex ratio in humans may be modified by certain nutritional and nonnutritional factors. The aim of this literature review is to explore the influence of maternal nutritional factors on sex ratio at birth in various animals and humans. We used Google Scholar, Research Gate, ProQuest, Scopus, Cochrane, and PubMed databases to collect appropriate articles for the review without limiting the publication period. Of the different nutritional approaches in animals the most frequent manipulations are controlling the energy intake and, to a lesser extent, the composition of the diet in terms of macronutrients and micronutrients is most likely to influence the sex ratio at birth in animals. The data on these factors affecting sex ratio at birth are sparse and offer little promise of influencing sex at birth in humans.