Nutrients delivered to the body build its tissues and regulate the processes that take place in it. Individual nutrients as well as dietary patterns as a whole may have an impact on the quality of semen and male fertility [22,23,24]. As far as insulin resistance is concerned, nutrition is a key element of therapy. In terms of the diet of people insulin resistance, it is important that they eat regularly in addition to maintaining the proper the composition and volume of meals [25]. The main dietary recommendations aimed at preventing insulin resistance include the following: eating plant-based fiber sourced from products, such as oats, beans, peas, lentils, grains, seeds, fruits and vegetables, whole grain bread, brown rice, and pasta; daily consumption of at least five servings of fruit and vegetables; limiting the consumption of fat (especially saturated fatty acids); limiting the consumption of fried foods, sweetened drinks, and sweets as well as foods rich in fat and sugar; eating breakfast; controlling the portion size of meals and snacks, and the frequency of eating; limiting alcohol consumption [26].

Studies often compare the “healthy” diet with the “Western” diet. Gaskins et al. equates the “Western” diet with the consumption of processed meat products, butter, dairy, refined grains and sweets, and a low consumption of vegetables and fruit. The “healthy” diet, on the other hand, which the authors describe as “prudent”, is characterized by a high consumption of vegetables and fruit, fish and poultry, soy, low-fat dairy products, oils, and whole grain products. The results of the study show that men who keep the “moderate” diet exhibit greater sperm motility [27]. In their study, Oostingh et al. showed a positive correlation between healthy dietary patterns and sperm concentration, its motility, and total count [28]. A study performed by Liu et al. connected the “Western” dietary style with a reduced sperm concentration and worse morphology [29].

Epidemiological studies indicate that the consumption of saturated fats is associated with the presence of markers of insulin resistance [30,31]. Moreover, some studies concerning the quality of semen also focused on particular groups of food products. These indicate a correlation between the frequency of consumption of processed meat products and a lower total sperm count, worse sperm morphology, lower semen volume, and a lower percentage of progressive motile sperm [32,33]. Different conclusions were drawn by Maldonado-Carceles et al., who showed that in all probability, meat consumption does not have an impact on the quality of semen; the frequency of consumption of offal, however, was correlated with lower sperm motility, while the frequency of consumption of crustaceans was positively correlated with sperm motility [34]. Moreover, studies show that the consumption of saturated fatty acids (SFA) and trans fatty acids has an adverse effect on the quality of semen. SFA consumption is negatively correlated with the total sperm count and concentration, while the consumption of trans fatty acids is negatively correlated with total sperm count [35,36,37].

Some scientists also focus on the assessment of particular diets that may improve the quality of semen. The Mediterranean diet is one of those that could be recommended in the context of the lifestyle of men with reduced semen quality, owing to the large contents of vegetables and unsaturated fatty acids, as well as fish. A positive effect of the Mediterranean diet on the quality of semen was shown in studies performed by Karayiannis et al., which indicated a relationship between the diet in question and increased sperm concentration, total sperm count, and progressive motile sperm count [45]. In their study, Cullitas-Tolin et al. also found a positive relationship between following the Mediterranean diet and an increased total sperm count [46]. Another diet worth considering is the DASH diet. Initially created for people with hypertension or at risk for it, it turns out to have a positive impact on the quality of semen [47]. In their study, Cullitas-Tolin et al. showed a positive relationship between the value of the DASH indicator and sperm concentration, total sperm count, and total progressive motile sperm count [46]. Other studies also show a positive correlation between the DASH indicator and higher normal sperm counts as well as the impact of the DASH diet on the increase of the antioxidative potential, which may alleviate changes in semen resulting from oxidative stress [48,49,50]. It needs to be emphasized that both the DASH diet and the Mediterranean diet are also indicated as the most beneficial ones in terms of the treatment and prevention of insulin resistance [51,52,53,54]. The use of the Mediterranean diet was associated with lower HOMA-IR values, lower insulin levels, and greater insulin sensitivity [52]. The DASH diet combined with a change of lifestyle showed improvement of insulin sensitivity [55].

Studies of the quality of semen often determine the patient’s Body Mass Index (BMI). This is the most basic indicator used in research to divide the study group according to the participants’ anthropometric characteristics. Eisenberg et al. showed a positive correlation between body mass and abnormal semen volume and concentration. In this study Only 6% of men with normal BMI were oligospermic, and in the group of obese men—17% were oligospermic [62]. When studying the impact of body mass on the quality of semen, Hammiche et al. found a negative impact of overweight on semen volume, concentration, and total progressive motile sperm count [63]. Fariello et al., on the other hand, determined that among overweight people, a larger percentage of DNA was damaged, in comparison to the control group [64].

Obesity, as determined by BMI, is often connected with insulin resistance. The body composition indicators that determine obesity, such as high percentage of body fat, waist circumference, and subcutaneous adipose tissue content, as well as the incidence of the metabolic syndrome in men, studied by Gobato et al., correlated with the occurrence of insulin resistance [4]. Thus, it is unsurprising that in studies performed in children, obesity and insulin resistance are described as factors that significantly increase the risk of metabolic diseases in adulthood [65].

Data concerning physical activity in the context of its effect on the quality of semen is conflicting. Although some studies indicate that it has no impact [66], most confirm a beneficial influence of recreational physical activity on the quality of semen both among healthy and infertile men [67,68,69,70]. For example, Danielewicz et al. found a positive correlation between the level of physical activity and sperm count (ΔT3-T1 = 69.4 mln/ej, ptrend = 0.043), progressive motile sperm count (ΔT3-T1 = 8.5%, ptrend < 0.001), and morphologically normal sperm count (ΔT3-T1 = 2.8%, ptrend = 0.003). In addition, coupled with the DASH diet, physical activity positively correlated with sperm concentration, total sperm count, progressive motile sperm count, and morphologically normal sperm count [22].

Scientists also focused on studying particular sport disciplines, or a particular type of physical activity. In their studies, Maleki and Tartibian showed that resistance exercises have a positive effect on reducing inflammation in the body as well as the level of oxidative stress, which correlates with improved semen quality and reduced percentage of damaged DNA [70]. In a study by Gaskins et al., weight training and open air exercises were proved to be beneficial for sperm concentration [68]. It is possible that the impact of weight training on improved seminological results was due to the fact that a moderately intense strength training influences the level of testosterone shortly after exercise and plays a role in reducing insulin resistance in healthy adult men [71].

Other studies showed a negative effect of a particular physical activity on the quality of semen—such were the conclusions of studies on the influence of cycling on the quality of semen [67,72]. Excessive physical effort, regardless of the discipline, seems to have a negative impact on the quality of semen [67]. This may be connected with the antioxidative capacities of the body, which can be reduced in men who train intensively, in comparison to men who train for recreation [70].

Physical activity is one of the factors that reduces insulin resistance. Studies performed in overweight or obese children and adolescents showed a positive effect of cardio training, particularly aerobic, on insulin resistance. Such exercises reduced both fasting insulin levels and the HOMA indicator values [71]. Similar relationships were found in studies in adults, i.e., after 8 weeks of aerobic exercise, reduced levels of fasting glucose and insulin were found in type 2 diabetes patients [73]. Hence, by treating the effects of metabolic disorders or preventing them—through the introduction of regular physical activity as early as at a young age—the quality of semen in the population can be improved.

Sleep, as the state when our bodies regenerate, also seems to have an effect on the quality of semen. Poor sleep quality is observed particularly among shift workers, who disrupt their natural circadian rhythm, and usually sleep in short several hour-long segments [74]. A study by Chen et al. showed that too much or too little sleep, as well as poor sleep quality, affect semen quality. According to the researchers, the optimum sleep duration beneficial for the quality of semen is 8–8.5 h [75]. Similar conclusions were drawn by Vigano et al., whose study showed a reduced semen volume in the case of men who had problems with falling asleep, with obesity and tobacco smoking as additional factors worsening the results [76]. A study by Du et al. is also worth mentioning—it showed that poor sleep quality in men was connected with lower total motility, concentration, progressive motility, morphologically normal sperm, and total sperm count [77]. This may be connected with melatonin concentrations in the body, whose urine levels correlate positively with sperm concentration and cellular oxidative DNA damage repair capacity [78].

Another phenomenon that often coexists with obesity is sleep apnea. It also has an impact on the quality of semen. Studies show that the incidence of sleep apnea correlates negatively both with testosterone concentration and erectile dysfunction. Sleep apnea is obviously connected with obesity, but its negative impact on the quality of semen is also thought to be connected with poor sleep quality, which disrupts the nocturnal testosterone rhythm [79].

Many hormones and enzymes are secreted in the diurnal rhythm, with the process engaging circadian and homeostatic mechanisms. A badly slept night may disrupt the secretion of hormones, such as cortisol or growth hormone (GH), which influence insulin secretion. With insufficient sleep, increased GH secretion is observed, contributing to a reduced glucose uptake in muscles, which in turn leads to insulin resistance [80]. Thus, sleep hygiene seems to be important both for fertility improvement and prevention of metabolic disorders.

Stress causes many negative processes in the body yet our health is strongly connected with it [81]. Mental stress causes disorders of secretion of hormones responsible for male fertility, thus lowering the quality of semen [78]. This influences semen quality via neuroendocrine factors, i.e., an increased level of glucocorticoids leads to decreased rates of testosterone excretion from Leydig cells, which impairs spermatogenesis [82]. It also causes oxidative stress in the body, in addition to exacerbating insulin resistance and inducing the proinflammatory cytokine cascade—with all these aspects having a negative impact on the quality of semen [83,84].

A study by Zou et al. showed that high levels of work-related stress have a negative effect on semen parameters, such as sperm concentration and total sperm count. The study also confirmed that the negative impact on the quality of semen is not observed in men who experienced high levels of social support as a means of alleviating stress [85]. As far as everyday stress is concerned, similar conclusions were drawn by Janevic et al., whose study connected perceived stress with reduced sperm motility, sperm concentration, and the percentage of morphologically normal sperm [86].

Everyday stress is not the only type that can influence the quality of semen. Studies show that persons exposed to sudden, intense stress also have reduced semen parameters [87,88]. For instance, some of the parameters of semen of men rescued from the 2008 Wenchuan earthquake were disrupted as late as 3 years after the event. According to the researchers conducting the study, this could be related to the post-traumatic stress disorder caused by the loss of a close person or property [88].

A common issue related to attempts at reducing stress are psychoactive substances. Alcohol and cigarettes have been studied numerous times in terms of their influence on the quality of semen [90,91]. As far as tobacco is concerned, studies unanimously confirm that it has a negative impact on semen volume, sperm concentration, sperm motility, morphology, and total sperm count, as well as the levels of follicle stimulating hormone and free testosterone [90,92]. Men who smoke cigarettes are also at risk of increased fragmentation of semen DNA [93]. In addition, tobacco smoking increases the risk of insulin resistance and hyperinsulinemia, thus increasing the risk of cardiovascular diseases [94].

In terms of alcohol, it reduces morphologically normal sperm count and causes sperm DNA damage [92,95]. Moreover, certain studies show its negative impact on fertility [96,97]. Moving beyond the direct impact of the aforementioned psychoactive substances on the quality of semen, it should be remembered that both excessive tobacco smoking and alcohol consumption contributes to an increased secretion of Reactive Oxygen Species (ROS)—inducing inflammation in the body and destroying the balance between ROS and antioxidants [94,95,98].

As mentioned, the duration of sexual abstinence prior to the examination of semen quality, as recommended by the WHO, is 2 to 7 days [3]. It is difficult to determine the ideal duration of sexual abstinence for optimum results of semen quality assessments due to the fact that some of its parameters improve while others worsen over time [99].

In the case of semen volume and sperm count, the following regularity can be noted: the longer the abstinence, the higher the levels of these parameters, with a particular increase in their values occurring after over 5 days of abstinence [100]. In the case of parameters, such as morphology, motility, and DNA fragmentation, it seems true that they improve after a shorter abstinence time (up to 4 days) [99].

Among men with insulin resistance, particularly in the group of obese persons, sexual abstinence is sometimes prolonged. This results from decreased libido, caused by deficiencies in sex hormones, especially testosterone, as well as abnormal androgen-estrogen ratios [101]. This fact also constituted a psychological burden; hence, it is again connected with an increased risk of semen quality disorders and infertility.

Care for the natural environment also helps to maintain health. Pollutants are regularly emitted to the atmosphere, soil, or water, entering our bodies through the respiratory and the digestive systems [102]. Scientific studies examine various substances originating from the external environment that have an adverse effect on male fertility. Among the pollutants in the environment that have an effect on the quality of semen, the following can surely be mentioned: phthalates [103], arsenic [104], perfluorinated compounds [105], dimethyl arsenic acid [106], ambient fine particular matter [107], ozone pollution [108], bisphenol A [109], parabens [110], organophosphate pesticides [111], and heavy metals [112]. Unfortunately, these substances are ubiquitous, thus being impossible to fully eliminate. Over the years, several studies have been performed that linked pollutants to insulin sensitivity markers [113,114,115,116]. The strongest evidence for a positive association between exposure to environmental pollutants and insulin resistance was shown in the case of phthalates and air pollutants [115,116].