Location

The present work was carried out in the Nutritional Physiology Laboratory and Experimental Surgery of the Agriculture Academic Unit, belonging to the Autonomous University of Nayarit.

Obtaining and nutritional features of pork

70 kilos of Yorkshire-Landrace breeds were used, fed free access with a diet that included 10 % avocado flour (LAF), for a period of 56 days until the fattening, in accordance with the recommendations of the Mexican Official Standard ^{NOM-062-ZOO-1999}. The avocados of the Hass variety (Persea American Mill) included in the pig diet were from discarding commercial by its size, without demereing its nutritional value (Lemus et al.,²⁰¹⁷). The loins used were characterized in an earlier work (^{Lemus-Avalos et al., 2020}), as a very similar chemical composition meat product, with low intramuscular fat content (5.94%), with 20.93% protein, 10.98 μg/G of γ-tocopherol, 3128 mg of gallic acid/100 g of total phenols. Also, with a high antioxidant activity analyzed with the radical assays DPPH (2,2-diphenyl-1-picrilhydrazyl, D-9132) (477.16 μm trolox/100g) and the radical ABTS (2.2'-azino-bis acid (3-ethylbenzotiazolin) -6-sulfonic, A-1888) (1054.55 μm trolox/100 g). It is a low beef in SFA, including palmitic (C16: 0) (21.93%), which is recognized as the highest saturated fat in pork, with a greater amount of arachid (20: 0) (0.45%). With a high content of polyunsaturated fatty acids, where cis (alpha) essential fatty acid (alpha) (18: 2 N6) represents 12.91%, as well as a high content of PFA (13.82%), so it has a high relationship of PFA/SFA (0.45%) and PFA/MFA (0.25%).

Individuals of study

For the study, 20 male adult participants were chosen between the ages of 30 to 60, with a BMI (body mass index) between 27 to 33 kg/m², without a history of cardiovascular disease. They must be intake pork on average once a week, without realization of physical activity, without use of food supplements with omegas fatty acids, no smokers, as well as accepting in writing to participate in the study. This research is attached to the declaration of Helsinki, to General Health Law and has approval from the Nayarit Bioethics State Commission (Nayarit's CEBIOÉTICA) in the trade number 88/CEB/2018, NO/17/2018.

Two study groups were formed; both consumed daily 100 g of pork loin fed 10 % avocado flour (LAF). A group of 10 subjects (group A), consumed it 4 weeks. The other (group B) integrated with 10 subjects, consumed it for a period of 6 weeks. The nutritional history of the individuals was obtained by means of a direct survey.

Diet

Participants were trained to meet during the experiment the recommendations of a balanced feeding according to WHO (^{OMS, 2017}), based on healthy diet characteristics. Advice for the Food Plan was individually, according to the weight, size and age of each subject, in accordance with the FAO Recommendation (^{Carbajal, 2013}), was included in its usual diet, the intake of the pork loin provided in the study.

Anthropometric parameters

The anthropometric evaluation was used to determine the body composition and diagnosed the degree of obesity, using the body mass index (BMI) and the obesity classification proposed by the World Health Organization (^{OMS, 2020}). The anthropometric measurement was performed at the beginning and end of each period in both groups, using a Tanita^® brand scale with a sensitivity of ± 100 g, and a digital scale with Bluetooth Bennet^® brand. The weight measure was obtained in lightweight and without footwear clothing, and by method of bioimpedance the percentage values of visceral fat and percentage of body fat. With the tape measure, dry brand fixed to a smooth wall, the height (cm) was obtained, respecting the plane of Frankfurt (Porion-Infraorbital) parallel to the ground and the horizontal bipupillary line, supporting the horizontal bar of the statement on the scalp (^{Martínez and Ortiz, 2013}). The BMI was calculated as the reason between the weight in Kilograms and the height squared in meters, considering overweight as an BMI equal or higher 25 (^{OMS, 2017}).

For the obtaining of the waist perimeter (cm) and hip (cm), the Lufkin® metallic tape measured, all measurements were performed using internationally accepted techniques (^{Marfell-Jones, M. (ISAK) 2001}). The waist perimeter (cm) was divided between the hip (cm) to obtain the waist/hip indicator (WHI) as an indicator of the adipose tissue distribution, this indicator is an independent predictor of risk and morbidity factors. It was considered moderate of 0.90 to 0.95 and high higher than 0.95 (^{Poirier et al., 2006}).

Profile of serum lipids

In both groups A and B, blood samplings were held to the participants at the beginning and at the end of the period of four or six weeks of LAF consumption. The sample was obtained from the antecubital vein after 12 hours of fasting; a baseline blood sample of 7 ml was collected in a dry tube. Each sample was placed in test tubes and centrifuged at 4,000 rpm for 10 minutes after which the serum was extracted. For the determination of serum concentration, they were measured with byosistem model A160. Getting measurements of: Glucose mg²/dL, (TC) Total cholesterol mg/dL, (TG) triglycerides mg/dL, OGT (oxalacetic glutic transaminase) U/L, HDL cholesterol (high density lipoproteins) mg/dl, HbA1c (Glicada hemoglobin) %, LDL cholesterol (low density lipoproteins) mg/dL, was calculated from TC, GT and HDL using the Friedewald formula (LDL = TC-HDL-GT/5) provided that GT <400 mg (^{Troyo-Barriga, 2004}). To estimate the value of the VLDL cholesterol 5 (mg/dl) divided (very low-density lipoproteins) mg/dl, the triglyceride concentration (^{D’Isa et al., 2013}).

Statistical analysis

With anthropometric data and serum lipid profiles obtained, descriptive analyzes and comparison between variables were performed, using quantitative analysis with paired T, to compare in each group the differences between the start and final periods of LAF consumption. A qualitative analysis was also performed in the variables of the serum profiles, a qualitative analysis by means of the X2 test, comparing the proportions according to the low levels (b), (n) normal or (a) tall in each group comparing the differences Among the start and end period of LAF consumption. For the analysis, the SPSS® STATISTICS 20 (^{SSPS, 2011}) software was used.

Anthropometric parameters

This study was designed to evaluate the effect in two LAF consumption periods over anthropometric and serum lipid profiles in overweight people. It was observed that all study participants declined significantly body fat, BMI, showing that when the consumption period of LAF is increased six weeks (Group B), better results were also decreased, visceral, and waist variables. This could be explained by the linoleic acid content of the flesh, considered essential fatty acid that benefits the reduction of body fat (^{Arenas and López, 2009}) and body weight (^{Sanhueza et al., 2002}).

^{Celada et al. (2015)} studied people with cardiovascular risk, added meat products, where animal fat was replaced by a combination of olive oil, flaxseed and fish, in three periods of 4 weeks each, reported a decrease in body fat, a waist -hip ratio and waist perimeter. In the fat reduced feeding period and the BMI was reduced, improved the ideal weight in the diet period enriched with fatty acids. These reports coincide with the study carried out here since the anthropometric parameters in individuals consume functional foods also decrease; what suggests that the intake of meat products with less fat or enriched with UFA, improves anthropometric markers, being able to reduce the risk to develop CVD.

There is a correlation between BMI and percentage of body fat (PBF). According to this, it can understand the decrease in BMI when lowering the PBF. Likewise, it was determined that the prevalence of visceral adipose tissue is related to BMI and hip circumference (^{García et al., 2016}). The increase in abdominal adipose tissue (visceral), promotes greater synthesis and release of adipocine in addition to leptin, resistin, angiotensinogen, pro-inflammatory cytokines (tumor necrosis factor [TNF] -α, interleukin [IL] -6, inhibitor of the Plasminogen activator Type 1 [PAI1]) and quemochinas. It can deteriorate Lipid and Glucidic metabolism through the increase in insulin resistance, and increase cardiovascular risk, so measuring the waist/hip index (WHI) is useful in the prediction of cardiometabolic risk ^{Hernández-Rodríguez et al. (2018)}.

According to ^{González-Acevedo et al. (2013)} changes could be due to the supplementation with UFA inhibits pre-adipocytes differentiation and increases the apoptosis of these cells, as well as intervene in regulation on the sympathetic nervous system, in the production of leptin and adiponectin. This function is manifested with the regulation of body fat that leads to changes in the distribution of fat-free mass ratio (^{Parra and Hernández, 2017}).

Profile of serum lipids

It was observed that the consumption of LAF, in the individuals of Group A (4 weeks) significantly decreased TG, VLDL levels and increased LDL. The values of the individuals of Group B (6 weeks) are also shown, observing significant differences in the decrease in glucose.

Better results are observed when consumed for longer (6 weeks) of LAF because a greater number of favorable health variables were modified. The content of essential fatty acid cis of the meat consumed can be associated with the antiathyrogenic effects found, due to its hypocolesterolemic and hypotrogracyreidemic action (^{Sanhueza et al., 2002}). As well as the phenolic compounds of the flesh due to its antioxidant properties that play an important role in the prevention of diseases such as cardiovascular disorders, type two diabetes, among others (^{Zapata et al., 2014}).

Similar results reported ^{Petzke et al., (2011)}, in a study conducted in young, healthy and normal weight women who consumed daily 200 g of pork for four weeks, observing that total cholesterol concentrations (- 7 %), LDL cholesterol (-8 %) and glucose (-4 %). ^{Delgado-Pando et al. (2014)}, they conducted a study on 22 volunteers to evaluate the consumption effect of Frankfurters sausage and Pate, reduced in fat and enriched with Omegas, after use in 3 periods of 4 weeks, with breaks between them of 4 weeks; finding decrease in c-LDL, Rusty c-LDL and c-LDL/c-HDL ratio in participants. Similar results observed ^{Maciá et al. (2005)}, when they studied people with hypercholesterolemia (18 women and 18 men), consumed 100 g/day of Iberian Ham of acorn and Olive Oil, the participants presented a decrease in total cholesterol, triglycerides and LDL cholesterol when they were consumed so much PFA as an Iberian ham of acorn, remained with normal HDL levels.

The results presented in this investigation, coincide with what is observed by ^{Pastoriza et al. (2017)}, who carried out a study with the intake of a functional food and observed that participants reduced blood glucose levels significantly due to catechins present in the diet and their action on enzymes for the control of post-pandary hyperglycemia.

For TG our results coincide with ^{Díaz-Perilla and Toro (2004)} who evaluated a diet rich monounsaturated fat for 4 weeks that significantly reduced triglycerides by 18.1 %. It is considered that the effect is greater if part of hypertriglyceridemia compared with normal levels of triglycerides (^{Leslie, 2007}), the same effect that could be produced in this work.

In the meta-analysis of (^{López-Huertas, 2012}) it is concluded that there is sufficient evidence to affirm that the intake of dose> 1g of UFA in patients with metabolic syndrome for at least 3 months produce a significant reduction of plasma triglycerides in a variable range between 7-25 %.

The presence of phenolic compounds, including flavonoids, could explain the hepatoprotective effect shown by the consumption of LAF due to its demonstrated antioxidant activity, because of a combination of its iron chelating properties and free radical sequestrators (^{Bermúdez-Toledo et al., 2014}). In addition to the phenolic compounds present, in the LAF, other natural antioxidants with immunomodulatory effects, anti-inflammatory, antifibrotic, free radical sequestrators and membrane stabilizers. They could contribute to protecting the liver of degenerative changes. As well as the presence of γ-tocopherol and its 2,7,8-trimethyl-2- (β-carboxietyl) -6-hydroxicroman metabolite have already been demonstrated to have anti-inflammatory activity (^{Fernandes et al., 2011}), by the inhibition of the enzymatic activity of cyclooxygenase-2 (COX-2), (^{Muñoz-Velázquez et al., 2012}).

Some authors consider that a balanced and adequate dietary intake can play a beneficial role when the profile of lipids in the blood is unfavorable and suggest that the risk of dyslipidemia can be modified according to the type of fat ingested (^{Peou et al., 2016}). It considers that oleic fatty acid present in avocado, can play an active role in the reduction of cholesterol and triglycerides in plasma, as well as reduce the C-LDL without greater change in c-HDL, reducing the risk of CVD.

Decreasing the consumption of nutritional sources with SFA helps prevent the development of Diabetes Mellitus type 2 (^{Mirmiran et al., 2018}). A review study published in 2017 reported that subjects who have a low diet in SFA showed better anti-inflammatory profiles, or at least one proinflammatory response (^{Rocha et al., 2017}). These findings suggest that the consumption of food with UFA (unsaturated fatty acids), contributes to improve inflammatory state and consequently prevent the development of insulin resistance, diabetes and cardiovascular disease.

It is considered in this study that food treatment was modified with respect to fatty acids in the same way as in other studies, (^{Jiya et al., 2015}). The profile of fatty acids in monogastric animals is almost a direct reflection of the fatty acids of their diet. Therefore, the LAFs that were consumed by the participants contain SFA preferably modified by UFA, managing the lipid profile (^{Lemus-Avalos et al., 2020}). By using pork fed with avocado, it is not only incorporated into the meat for human consumption PFA but also, antioxidants that can benefit the health to the consumer (^{Hernández-López et al., 2016a}; ^{Hernández- López et al., 2016b}).