Effects of Different Types of Flaxseed Flour in Appetite and Satiety Sensations Among Overweight and Obese Women

Obesity is a chronic multifactorial disease and its high growth poses a challenge to public health worldwide. It is estimated that 2.1 billion adults are overweight, representing 27,0% of the world population1. During the last three decades in Brazil, the growth of overweight and obesity has been higher among women than among men. According to recent data, almost 50% of the populations aged over 20 years are overweight and obese2. Obesity results from excessive calories intake and reduced energy expenditure and is influenced by genetic, psychological, environmental and physiologic factors3. Although changes in lifestyle, starting by adopting healthy eating habits, are considered the first intervention in the treatment of obesity, it is necessary to look for foods that promote weight loss for the effective treatment of obesity, such as flaxseed flour, which is composed of polyunsaturated fatty acids of the series n-3 and n-6, protein, and soluble and insoluble fibers4. International Journal of Cardiovascular Sciences. 2016;29(1):37-46


Introduction
Obesity is a chronic multifactorial disease and its high growth poses a challenge to public health worldwide.It is estimated that 2.1 billion adults are overweight, representing 27,0% of the world population 1 .During the last three decades in Brazil, the growth of overweight and obesity has been higher among women than among men.According to recent data, almost 50% of the populations aged over 20 years are overweight and obese 2 .
Obesity results from excessive calories intake and reduced energy expenditure and is influenced by genetic, psychological, environmental and physiologic factors 3 .Although changes in lifestyle, starting by adopting healthy eating habits, are considered the first intervention in the treatment of obesity, it is necessary to look for foods that promote weight loss for the effective treatment of obesity, such as flaxseed flour, which is composed of polyunsaturated fatty acids of the series n-3 and n-6, protein, and soluble and insoluble fibers 4 .
Studies show that eating foods rich in fiber is associated with prevention and treatment of obesity and reduced risk for developing cardiovascular diseases 5 .The structure, c h e m i c a l c o m p o s i t i o n , concentration and molecular weight of dietary fibers are i m p o r t a n t f a c t o r s a n d determine the degree of viscosity of dietary fiber, influencing increase of satiety and reducing appetite and food intake 6,7 .However, the effect of fiber on satiety and food intake was not seen in a systematic review published a few years ago 8 .
The aim of this study was to compare the effects of three different types of flaxseed flour -whole brown flaxseed flour (WBFF), brown defatted flaxseed flour (BDFF) and golden flaxseed flour (GFF) -in the subjective sensation of appetite and satiety in overweight and obese women.

Methods
The study was approved by the Research Ethics Committee of Hospital Universitário Clementino Fraga Filho da Universidade Federal do Rio de Janeiro (HUCFF/UFRJ) under no.205/08.All volunteers signed an Informed Consent Form according to Resolution CNS 466/12.
A randomized clinical trial was conducted with adult women of any ethnicity.Women who were nursing, diabetic, menopausal, smokers and using anorectic drugs during the last three months were excluded from the study.
The volunteers were recruited through advertisements on major newspapers.The first visit was scheduled for evaluation of inclusion/exclusion criteria at Centro de Pesquisa em Nutrição Clínica da Universidade Federal do Rio de Janeiro (CEPNUC/UFRJ) located at HUCFF/UFRJ.A structured questionnaire developed by the researchers was applied in order to obtain general information such as age, socioeconomic status, self-reported skin color, smoking and use of medications.
Once recruited, the volunteers went to CEPNUC/UFRJ in the morning of the following week after fasting for 8 hours, to conduct the clinical trial.The clinical trial consisted of breakfast, composed as follows: 2 cups of nonfat yogurt with 200 g each, plus a complement of 30 g of flaxseed flour or 14 g of soluble fiber or just the yogurt, without any complement.
In the anthropometric evaluation, body mass (kg) and height (m) were measured using a digital platform attached to a Filizola ® stadiometer (São Paulo, Brazil), according to Gibson 9 and nutritional diagnosis according to body mass index (BMI) 10 .
Participants were stratified according to BMI into three groups: overweight, grade 1 obesity and grade 2 obesity 10 .The individuals were randomly assigned to different test meals as follows: yogurt with 30 g (two tablespoons) of whole brown flaxseed flour (WBFF); yogurt with 30 g of brown defatted flaxseed flour (BDFF); yogurt with 30 g of golden flaxseed flour (GFF); yogurt with 14 g of soluble fiber (guar gum) (Nestlé ® ) and just yoghurt without any complement (control).The BDFF and GFF groups had their soluble fiber (guar gum) increased by 2.0 and 4.0 g, respectively, in order to match the amount of 12 g of dietary fiber in all complements (Table 1).
Appetite and satiety sensation was evaluated using an adaptation of the visual analogue scale (VAS) 11 in which the volunteers answered two questions: "How hungry do you feel now?" and "Do you feel satisfied?How much?".The purpose of the answer was to grade their appetite and satiety sensations, marking it on a 0-10 cm line, where the left end represented "I am not hungry at all"/"I am completely empty" and, on the right end, "I have never felt so hungry"/"I cannot stand to eat anything else", respectively.The quantification of the grades was performed by measuring the distance from the left end to the volunteer's labeling.
In this study, the VAS, originally consisting of eight questions, was adapted, using only two questions in the scale: "How hungry do you feel now?" and "Do you feel satisfied?"How much?", because we believe that these questions pinpoint the most important opposing physiological effects about the appetite of overweight and obese individuals.
The individuals, still fasting, filled out the first VAS (T0) immediately before having breakfast.After eating breakfast, the VAS was filled out at 15 (T15), 45 (T45), 75 (T75) and 105 (T105) minutes.WBFF -whole brown flaxseed flour; BDFF -brown defatted flaxseed flour; GFF -golden flaxseed flour; Fiber -soluble fiber; Control -yogurt Predicting a rapid decline in the sensations of appetite and quick increase in the sensation of satiety after breakfast and until 15 minutes (T15), we calculated the rate of variation between times T0 and T15 for the scores on the VAS for appetite and satiety.That period was named post-immediate.
For the subsequent times (T45, T75 and T105), steady increase in the sensation of appetite and decreased sensation of satiety over T15 were predicted.Then, we calculated the rate of variation for the period T15-T105 obtained by simple linear regression (slope of regression).This period was named post-late.The VAS scores at the five times (T0, T15, T45, T75 and T105) produced two variable answers named post-immediate (T0-T15) and post-late (T15-T105), whose units are expressed in "cm/15 minutes".
Additionally, for both the scale of appetite and for the scale of satiety, and from the average rates of variations calculated (post-immediate and post-late), the volunteers were classified into four groups according to the quadrants formed by the values above and below the mean rates of variation: 1) LQ-GQ: loses quickly and gains quickly; 2) LQ-GS: loses quickly and gains slowly; 3) LS-GQ: loses slowly and gains quickly; and 4) LS-GS: loses slowly and gains slowly.
The results were expressed as mean±standard deviation.
Analysis of variance (ANOVA) was used to compare the rates of post-immediate and post-late variation in the five groups.The correlations between the rates of postimmediate and post-late variation were obtained using the Spearman coefficient for the five groups and stratified by degree of obesity.The Spearman correlation coefficient was used to analyze the correlation between BMI (all volunteers) and the rates of variation according to the groups.
Statistical analyses were performed using the Statistical Package for Social Sciences for Windows (SPSS) version 17.0 and the results were considered statistically significant when p≤0.05.

Results
The study included 265 women: 70 in the overweight group, 95 in the grade 1 obesity group and 100 in grade 2 obesity group with mean age 38.1±4.9 and mean BMI 32.98±3.85kg/m 2 (Table 2).
The average scores obtained through the answers to the times T0, T15, T45, T75 and T105 are shown in Figure 1.The control group was the one presenting greater appetite and less satiety at all times in the clinical trial.In contrast, the groups receiving a complement of different flaxseed flours presented similar behavior in the sensation of appetite and satiety and the BDFF group presented less appetite and greater satiety.In addition, a rapid decline in the sensation of appetite and an increased sensation of satiety was observed between times T0 and T15.In contrast, from T15 and in subsequent times, a growing sensation of appetite and a decreasing sensation of satiety was observed.The behavior of these variables allowed calculating the rate of variation between the times T0-T15 and T15-T105, named post-immediate and post-late, respectively (Figure 2).The different complements at the post-immediate and post-late times regarding the feelings of appetite and satiety were compared according to the degree of obesity.
No statistically significant differences were observed, thus showing that the complements had similar effects in reducing appetite and increasing satiety for the three groups studied.
However, in the Spearman correlation between the postimmediate and post-late times (Table 3), BDFF complement presented a better effect in reducing appetite and increasing satiety in the overweight and grade 1 obesity group; however, this effect was not observed in the grade 2 obesity group.In this group, WBFF complement promoted the highest appetite growth rate and the complement did not induce any sensation of satiety in this group.
The effects of BDFF complement can also be seen individually (Table 4).In the division of the quadrants, the volunteers receiving BDFF complement, with respect to the sensation of appetite, appear more frequently in the LS-GS quadrant (overweight group 47.0% and grade 1 obesity group, 47.6%).For the sensation of satiety, the overweight group appears more frequently in the LQ-GQ quadrant (41.2%) and the grade 1 obesity group appears more frequently in the LS-GQ quadrant (31.8%).

Quadrants
Comparing the different complements with BMI on a continuous basis (Table 5), statistically significant results were not found, showing that the categorization of the variable BMI into three groups (overweight, grade 1 obesity and grade 2 obesity) did not influence the result.This also allows evaluating the influence of obesity on the sensations of appetite and satiety.

Discussion
Understanding the determinants of appetite by assessing the sensation of appetite and satiety, as well as understanding the foods that influence these sensations is essential because of their connection to the genesis and treatment of obesity, in an attempt to achieve a healthy weight 12 .
Obesity is a multifactorial disease and its high growth worldwide has aroused the interest of researchers about its etiology and treatment.In Latin American countries, including Brazil, the prevalence of obesity is increasing.The trends in early mortality due to cardiovascular diseases observed in the last decade in the Americas would indicate that these trends continue to increase 13 .Obesity is a public health problem and, in women, it is associated with increased risk of hypertension, metabolic syndrome, insulin resistance, dyslipidemia, cardiovascular disease, in addition to polycystic ovary syndrome, endometrial cancer and breast cancer 14 .
Nutritional intervention is a therapeutic strategy to combat overweight.Due to its chemical composition rich in series n-3 and n-6 polyunsaturated fatty acids, proteins and soluble and insoluble fibers, flaxseed flour can be used to control and combat overweight.It is important to emphasize that it was not possible to find studies investigating the influence of intake of flaxseed flour on appetite, or comparing the influence of different types of flaxseed flours on appetite and satiety in overweight and obese women.
Several pathways are involved in the body weight regulation system.Among these pathways, appetite, represented by the sensations of appetite and satiety, involves external factors (environmental) and internal factors (physiological), those that are related to postprandial satiety, given by bolus volume and gastric emptying 15 .Also, the role of white adipose tissues is enhanced based on their metabolic and inflammatory characteristics.There is an adaptive response that involves coordinated changes in the brain, gut, muscle, liver, adipose tissue, neuroendocrine system and peripheral signals.The hypothalamus and hindbrain are stimulated, hence increasing appetite and sending neuroendocrine efferent signals that influence appetite and energy expenditure 16 .
It is possible to consider appetite as a subjective and physiological sensation aroused by the food intake necessity.Satiety is the process developed during feeding and determines the cessation of food intake by antral distension of the stomach 17 .Glucagon-like peptide-1 (GLP-1) 7-36 amide, an insulinotropic hormone released from the intestinal L cells in response to nutrient ingestion, inhibits gastric emptying and gastric acid secretion.These effects of GLP-1 may be particularly important in the regulation of appetite and satiety in obese individuals 18 .
The association between appetite and satiety is present in both overweight and grade 1 obesity groups, which was evident in the responses related to reduction of appetite and increased satiety after eating breakfast with BDFF.However, this relationship was not observed in the grade 2 obesity group because the different complements were not able to reduce the sensation of appetite and increase the sensation of satiety in this group.Similar results were found in Adam and Westerterp-Plantenga 19 , who investigated the release of glucagon-like peptide and satiety after a study involving complementary nutrients comparing normal-weight and obese individuals 19 .
The degree of obesity may determine a lower response to the physiological signals of appetite and satiety, thereby promoting greater food intake due to exposure to chronic stress and depression, common in highly obese women 20 .It has been recently demonstrated, using neuroimaging, that foods are particularly rewarding when immediately available and particularly so when high in caloric density 21 .
Although the different types of flaxseed flours have not presented any effects on the sensation of appetite and satiety in the grade 2 obesity group, in the overweight and grade 1 obesity group, the chemical composition of BDFF seems to have had an important role in those sensations.It is noteworthy that all complements (except the control) had the same amount of dietary fibers, suggesting that the structure of dietary fiber and the amount of BDFF proteins may have favored the reduction of appetite and increase of satiety in this group.
Soluble fiber showed to have beneficial effects on satiety reduction and food intake and can increase speed of weight loss in obese individuals.However, the constitution and effects of dietary fibers are related to their structure, chemical composition, concentration and molecular weight, which causes thickening of food, called viscosity 22 .According to our results, Vuksan et al. 7 analyzed the same amount of dietary fiber intake (5 g) with different degrees of viscosity and concluded that the higher viscosity of the fiber smaller the food intake 7 .
Another important factor that may be related to appetite reduction and satiety increase is high consumption of proteins in the usual diet or after eating a meal rich in proteins 23 .The amount of proteins was 5.0 g, 7.6 g and 5.8 g in the WBFF, BDFF and GFF flours, respectively, suggesting that the higher content of protein in BDFF was able to help reducing the sensation of appetite and increasing the sensation of satiety in the overweight and grade 1 obesity groups.
Yoghurt only shows an effect on appetite when flaxseed flour is added.Therefore, from a practical point of view, the findings do not show the effect of yogurt, as the control group consuming just yogurt did not present this effect on satiety.Furthermore, our results demonstrate that the use of two tablespoons of brown defatted flaxseed flour prolonged the sensation of satiety, and the brown defatted flaxseed flour produced in Brazil is accessible to the population.Therefore, it can be said that a visible effect is produced by the brown defatted flaxseed flour.Considering the differences in the composition of flaxseed flour, the highest protein content of brown defatted flaxseed flour could have prolonged the sensation of satiety observed.
Some limitations are found in this study: the short time to evaluate the sensations of appetite and satiety after breakfast and the small number of individuals randomized for the fiber group among overweight volunteers.

Conclusions
This study suggests that 30 g BDFF complement for breakfast promotes greater reduction of appetite and increased satiety in the overweight and grade 1 obesity groups.This effect is probably produced due to the greater viscosity and amount of proteins in the flaxseed flour.In the grade 2 obesity group, the complements were not able to reduce appetite or increase satiety, suggesting that higher levels of obesity may interfere with control of satiety.However, further studies are needed to assess other factors related to appetite and food intake in grade 2 obese women.
In this context, our findings demonstrate that BDFF is an effective, safe, inexpensive and easily accessible food for the treatment of obesity, due to its positive influence over the subjective sensation of appetite.

Potential Conflicts of Interest
This study has no relevant conflicts of interest.

Sources of Funding
This study was partially funded by CNPq, CAPES and FAPERJ..

Academic Association
This manuscript is part of the Master's dissertation of Wânia Lúcia Araujo Monteiro from Universidade Federal do Rio de Janeiro.

Table 2 Characteristics of the study population by groups and complement Age (years) mean±SD White women (%) More than 12 years of study (%)
WBFF -whole brown flaxseed flour; BDFF -brown defatted flaxseed flour; GFF -golden flaxseed flour; Fiber -soluble fiber; Control -yogurt; SD -standard deviation

Table 3 Correlation between post-immediate and post-late times according to breakfast complementt in the groups studied r p
WBFF -whole brown flaxseed flour; BDFF -brown defatted flaxseed flour; GFF -golden flaxseed flour; Fiber -soluble fiber; Control -yogurt

Table 5 Correlation coefficient of BMI with sensations of appetite and satiety in the post-immediate and post-late times according to the complement#
#Spearman correlation WBFF -whole brown flaxseed flour; BDFF -brown defatted flaxseed flour; GFF -golden flaxseed flour; Fiber -soluble fiber; Control -yogurt; BMI -body mass index