1. Introduction
Although there is an open debate on whether considering obesity as a disease [
1], it is undeniable that excessive body fat accumulation, both overweight and obesity, have reached worldwide epidemic dimensions in the last decades as highlighted by the World Health Organization (WHO, Fact sheet 311) [
2,
3]. Worldwide, obesity has nearly tripled since 1975 despite public health policies and treatment efforts to combat the obesity epidemic [
4]. Estimations dating back to 2016-2017 projected that, if the increasing trend in obesity continued, by 2025, global obesity prevalence will reach 20% of the population [
5]. However, these figures were already surpassed in Europe in 2022 [
3].
Central obesity is a contributor of metabolic syndrome (MetS), a major risk factor for the development of chronic non-communicable diseases (NCD) such as type 2 diabetes mellitus (T2D), cardiovascular diseases (CVD) and many types of cancer [
6,
7]. In addition, the low-grade chronic inflammation commonly associated with obesity is also related to many of these and many other comorbidities (T2D, CVD, metabolic-associated fatty liver disease (MAFLD), steatohepatitis, osteoarthritis, iron deficiency, asthma, cancer, and neurodegenerative diseases) [
8]. Therefore, considering the increasing prevalence of obesity and its associated comorbidities, it is of utmost importance to further understand this metabolic condition and how it can be more effectively prevented.
Far more than an imbalance between food intake and energy expenditure, obesity is a complex multifactorial disorder resulting from the interaction of a range of conditions including lifestyle (mostly diet and physical activity), social and environmental aspects (obesogenic environment, country, religion, socioeconomic status, education), or biological factors (aging, sex, genotype, epigenetic modifications, microbiota composition), among others [
9].
For many years, dietary strategies to lose weight have consisted of varying macronutrient composition (e.g., low carbohydrate or low fat) as well as restricting total energy (e.g. low calorie, intermittent fasting) intake, whereas the reduction of body weight and body mass index (BMI) have been the main targets to determine the effectiveness of the weight reduction treatment. However, there has been a progressive shift on the approach to weight loss strategies and the focus on relevant endpoints [
10]. Changes in BMI have been largely considered as a key endpoint to measure success of the weight management strategies. BMI has been a population-level measure of overweight and obesity commonly used for both sexes and for all ages of adults; however, this index has also been largely criticised, as BMI value varies greatly among individuals based on age, sex, and ethnicity. Furthermore, BMI is not sensitive enough to differentiate the level or the distribution of adipose tissue mass with the health-related implications. Indeed, for any given amount of body fat, greater cardio-metabolic risk has been associated with the localization of excess fat in the visceral adipose tissue and ectopic depots (such as muscle, liver, and pancreas) [
11,
12].
In addition to the above, it is also important to consider the improvement of health as a relevant endpoint in weight loss treatments. While many types of dietary interventions can achieve a negative energy balance, a successful dietary strategy permits a loss of at least 5% of baseline body weight along with improvement on cardiometabolic health outcomes [
10]. Given the large variability between individuals in their weight loss responses to most treatments, it is essential that future research addressing the causes of such variability incorporates more rigorous analyses of the key factors involved, i.e. dietary composition and dietary patterns, energy requirements and energy expenditure (e.g., resting metabolic rate and physical activity energy expenditure) [
13].
In line with this, and to further increase in the success of weight-loss treatments, excess of body weight must be addressed with a multidisciplinary approach. Sex and age are very important factors in the individualization process due to critical differences in hormone concentration, adiposity, fat distribution [
14,
15], or even different eating behaviour and dietary habits [
16], as well as microbiota composition [
17]. Demographic factors (educational level, ethnicity, nationality, income level, occupation, etc.) are also associated to obesity on an individual and community level, and thus understanding the relationship between these factors is essential to implement changes/recommendations that may help to fight the obesity epidemic [
18]. All these aspects and complexity of their interactions suggest that there might be different subpopulations with different types of overweight/obesity and risk for other diseases, and thus with different optimal treatment response. More research must be conducted to determine their distinguishable features for subsequent risk and response stratification [
1]. In this context, nutrition advice based on the unique characteristics of an individual, emerged as a new strategy to improve the way obesity was being tackled. Personalized nutrition tries to take into account many of these multiple factors based on baseline information to then establish decisions and choose the most appropriate weight loss treatment [
19,
20].
All the above-mentioned features have been considered and reunited in GREENCOF, a research project aimed at improving our understanding of the potential beneficial regulatory effects of a coffee drink in subjects with overweight/obesity, with a multi-faceted approach. Coffee is one of the beverages most consumed worldwide, and due to its high content in (poly)phenols [
21] this beverage constitutes a major source of these bioactive compounds in Europe [
22]. There is a body of scientific evidence that supports the potential beneficial health effects of regularly consuming coffee, including weight management and cardio-metabolic effects [
23,
24,
25]. Nevertheless, the controversy remains as to whether these benefits are associated to the coffee (poly)phenols and/or to any other components of this drink. It is also unclear, whether the effects are equally produced in any individual drinking coffee or if a particular subpopulation may benefit best. GREENCOF will contribute to these issues by exploring the association between consuming coffee in volunteers with overweight/obesity with a focus on individual responses and the multiplicity of factors involved in the response.
The purpose of the current article is to evaluate the association between some of the main variables classically linked with overweight/obesity management studies: i) dietary intake, energy expenditure (‘causative variables’), ii) body weight, body fat distribution (‘measurement variables’), and iii) cardio-metabolic risk factors (‘outcome variables’) in subjects with overweight and obesity, with an insight into the variability of these factors in the study population and to understand among these factors which ones contribute the most to variability.
4. Discussion.
The current work aimed to contribute to our understanding of the variability and potential relationship between some of the main factors associated with overweight/obesity, i.e. food intake (both quantity and quality of the diet), energy expenditure (RMR and physical activity), body composition and cardiometabolic risk factors in a mixed (men and women) sample population affected with this disorder. Therefore, a holistic approach was used to comprehend the baseline characteristics in the studied population.
The initial characterization of the study population here presented corresponds to the baseline features of volunteers participating in a randomized, cross-over, blind, dose-response nutritional intervention to understand the effects of coffee bioactive compounds on overweight/obesity. In this nutritional intervention, special attention has been paid to address a wide range of factors potentially contributing to the inter-individual variability in the response to dietary bioactive compounds, specifically (poly)phenols. Thus, deepening into the main factors contributing to the variability of the population before starting the intervention would help to understand the factors involved in obesity and better explain the different response of these volunteers to the intervention with a slightly roasted coffee rich in (poly)phenols as a weight losing/health improving tool.
It is well known that diet is a key factor in obesity prevention and treatment. As aforementioned, current research addressing the factors causing inter-individual variability in response to dietary interventions incorporates rigorous analyses of dietary intake [
13]. As shown in the results of the present work, 27.1 % of participants underreported their EI. In line with this, previous studies support that people with overweight or obesity [
48,
49] tend to underreport their EI for different reasons: some underreport their food consumption deliberately, others forget some food or beverages once they are interviewed (memory bias), or they can reduce and/or modify their food consumption, or else make different food choices due to the Hawthorne effect, consisting in participants changing eating behaviour during the period of study due to being observed [
48]. A possible explanation to the higher CV values observed in the dietetic variables (apart from the interindividual differences naturally present in the volunteers) is the misreporting of the 24-hours of dietary recalls.
Another lifestyle factor that has been extensively linked to obesity and overweight, is excessive EI or elevated energy density of the diet, high consumption of foods rich in SFA or added sugars [
50,
51,
52,
53,
54], as well as unhealthy dietary patterns due to inadequate dietary choices [
51]. In the present study, participants’ diet was unbalanced, as the caloric profile did not meet the nutritional objectives for Spanish population [
39]. In addition, other nutritional objectives were not met (
Table 2 and
Table 3), such as daily dietary fibre intake, that was 14.5 g and 5.8 g lower than recommended intake for men and women, respectively (nutritional objective: 35 g/day for men and 25 g/day for women). When the nutrients intake was corrected by EI, dietary fibre intake per 1000 kcal continued to be below the recommendation (14 g per 1000 kcal for both sexes) [
39]. Regarding dietary cholesterol, daily intake was 338 mg (38 mg higher than recommended) and when corrected by EI, dietary cholesterol continued to be above the recommendation of 100 mg per 1000 kcal (mean value of 172 mg per 1000 kcal;
Table 3). The energy coming from lipids was also elevated (40.9 %) in detriment of carbohydrates (36.9 %). Fatty acids (FA) intake was also inadequate, as SFAs were above 10 % of total EI (12.6 %), mean α-linolenic acid intake was below 1 % of total EI (0.5 %) and mean linoleic acid was above 3 % (4.5 %). Moreover, the ratio between total ω6: ω3 FA was also unbalanced, 6.5:1 instead of being between 4:1 and 2:1 as recommended [
55]. Although most participants had moderate adherence to MD according to MEDAS questionnaire (74.6 %,
Supplementary Table S4), they had an inadequate lipid intake, high in SFA and ω6 and low in ω3 FA. These higher intakes of SFAs and ω6 has been observed in the Western dietary pattern [
56]. In addition, the high intake of SFAs and cholesterol might indicate that subjects’ diet was rich in animal products such as red and processed meat, or other foods rich in SFAs, to the detriment of foods that are sources of dietary fibre, such as vegetables, fruits, whole grains, and nuts as dietary fibre intake was lower than recommended [
50,
52,
56].
Regarding sex differences in diet composition, only total carbohydrate intake was different between men and women (
p = 0.038), but when expressed as the energy coming from carbohydrates, it did not reach the threshold of significance. Nevertheless, women showed a trend to a lower carbohydrate intake (
Table 2 and
Table 3). Furthermore, the percentage of energy coming from α-linolenic acid was significantly higher in women (
p = 0.029), but these differences cannot be considered clinically relevant (median values 0.49 % in women and 0.40 % in men; total α-linolenic acid in grams: 0.975 g in women and 0.920 g in men). These results dissent from previous studies describing that women consume more foods rich in carbohydrates and simple sugars, but men have higher consumption of food rich in fats [
57], or from other research showing that women in southern European countries consume more fruits, vegetables and, therefore, more dietary fibre than men who also had a higher fat intake [
37]. In this case, total dietary fibre intake and dietary fibre corrected by energy (g / 1000 kcal) were similar and lower than recommended for both sexes, as well as (poly)phenol intake (total and corrected by energy). These dietary indices and the subjects’ macronutrient intake may indicate that the consumption of fruits, vegetables, whole cereals and other sources of dietary fibre and (poly)phenols are low and homogeneous between both sexes (
Table 2).
Nonetheless, nowadays most authors agree that one dietary factor alone, or sole nutrients such as SFA or added sugars, should not be used to determine if a diet is healthy or not, as it is necessary to consider the dietary pattern as a whole to assess the influence of the diet in cardiometabolic or obesity risk [
54]. In agreement, interventional studies have shown that replacement of SFA with unsaturated fatty acids (UFA) might have limited effect in reducing waist circumference or improving serum lipid profile in metabolically healthy adults with overweight and obesity if caloric restriction is not achieved [
50]. Regarding sugar intake, intrinsic sugars and the percentage of energy coming from these sugars (
Table 2 and
Table 3), were similar to those described in the ANIBES study in a representative sample of Spanish population aged between 18 to 64 years old [
58]. Alike the results of the aforementioned study with SFA and UFA [
50], reducing free sugar intake must be accompanied with lower EI, as isoenergetic replacement with other carbohydrates is not significantly associated with changes in body weight [
53]. There is a body of evidence that supports that the Mediterranean diet may reduce cardiometabolic risk and obesity [
52,
59] and that lifestyle changes to balance EI and energy expenditure are more realistic strategies to treat the excess of body fat [
60]. The results of the present study show that participants’ diet was slightly deflected from the traditional Mediterranean diet, which is predominantly a plant-based and a low energy density diet. This outcome is agreement with studies that support that the Spanish population is moving away from the Mediterranean diet, with high meat consumption and low in foods that are sources of dietary fibre and (poly)phenols, which could be related to the increasing rates of cardiometabolic diseases in Spain [
61].
In nutritional epidemiology, factor analysis is a commonly used method to derive eating patterns [
62,
63,
64,
65]. Therefore, in the present study factor analysis was used to reduce dietary data collected with the 24-hour recalls into patterns based upon the inter-correlations between nutrients. Three factors emerged accounting for 51.0 %, 13.5 % and 10.5 % respectively (
Table 7). The first factor (the “Caloric and lipid risk factor”) was related to total lipid intake and lipid composition, as well as protein intake of the diet and EI, could be related to a high energy density diet. The second factor (the “Plant-based diet factor”) with total (poly)phenol intake, dietary fibre and intrinsic sugars as main loadings, could be a proxy for fruits, vegetables, whole cereals and other plant-based products, and it may be considered as a healthy pattern. The third factor (the “Dietary glycaemic factor”) was mainly formed by added sugars and total carbohydrate intake, and to a lower extent SFA, could be associated with a Western dietary pattern [
56].
In addition to dietary intake, the other key factor that must be considered for understanding inter-individual variability in weight loss is energy expenditure, which includes physical activity and resting energy requirements [
13]. Regarding physical activity, median METs values indicate that most volunteers had a sedentary behaviour (median METs values 1.12,
Table 6). This outcome was reinforced by individual PAL values (calculated as the ratio between TEE:RMR), which indicated that most participants had low levels of physical activity (mean PAL value 1.36) and only one subject had moderate physical activity levels (PAL value above 1.6), according to EFSA cut-off values [
30,
47]. These results agree with previous studies that showed that the prevalence of physical inactivity and sedentary behaviour is higher in adults with obesity. In fact, in a recent metanalysis an increased risk of obesity with sedentary behaviour and physical inactivity was corroborated [
45].
The negative impact in cardiovascular health of sedentary behaviour has been extensively described [
66]. As shown in a recent study, postprandial glucose, insulin and plasma TG diminished with regular bouts of physical activity after prolonged sitting, reducing cardiometabolic risk [
66]. Other mechanisms involved are related to enzymes that regulate lipid metabolism, such as muscle lipoprotein lipase (LPL), that are significantly reduced after long periods of immobilization, changes associated with lower levels of HDL, higher levels of TG and postprandial lipids [
67,
68]. As stated before, only a few dietary and physical activity parameters differ significantly between women and men, but these differences were not clinically relevant (
Table 2,
Table 3 and
Table 6). Other differences in body composition, biochemical measurements, or energy expenditure may be explained by sex-specific differences that are widely documented.
As expected, there were significant differences between women and men in anthropometric and body composition measurements (
Table 5). Due to hormonal dissimilarity and a higher expression of estrogenic and progesterone receptors in subcutaneous adipose tissue, women have more fat mass and a peripheral distribution of adiposity. On the contrary, men usually accumulate fat mass in the abdominal and thoracic area [
57]. Interestingly, in the present study female subjects had a significantly higher visceral fat area (VFA) than men (
p = 0.003) indicating a central distribution of adiposity. This elevated accumulation of fat in visceral tissues could be explained by the age of female subjects (median age 53 years), as visceral fat accumulation tends to increase due menopause and in postmenopausal women visceral fat represents nearly 15 to 20 % of total fat [
69]. Although, this excess of visceral fat can increase the cardiometabolic risk in postmenopausal women [
69], women did not exhibit a higher metabolic risk comparing to men when serum lipid profile, glucose metabolism or other measurements were analysed (
Table 4).
Regarding cardiometabolic sex differences, women showed higher HDL levels compared to men, which is related to sex hormones differences, mainly due to oestrogens [
70], and lower levels of transaminases (AST and ALT) and SBP (
Table 4). Transaminases, especially ALT, are markers of non-alcoholic fatty liver disease (NAFLD), recently termed as MAFLD. Moreover, elevated ALT levels had been associated with an increased risk of metabolic syndrome or insulin resistance [
71]. Other studies support that liver transaminases levels are associated with sex, specifically, men usually have higher levels of ALT [
71,
72,
73,
74]. In this study, although men had higher transaminases levels, both sexes had transaminase values within reference limits (
Table 4). SBP was also higher in men than in women, in accordance with previous research suggesting that the higher prevalence of hypertension in men may be due to interactions between oestrogens/testosterone and the renin-angiotensin-aldosterone system. Nonetheless, women appeared to have higher cardiovascular risk at lower blood pressure levels than men, and once menopause is reached, blood pressure increases at higher rates in women [
75,
76]. Considering these results, and due to the high prevalence of Metabolic Syndrome in this specific population (
Supplementary Table S5), participants might benefit from an intervention that could reduce their cardiometabolic risk or that could help controlling some components of metabolic syndrome.
When tackling overweight and obesity with a personalized approach, many factors may be considered [
20], thus it is important to understand the relationship between them and it may be convenient to transform a large set of correlated variables into smaller sets of non-correlated variables, called principal components or factors [
62,
63,
64,
65]. This analysis allows to identify the underlying structure in data matrix and describe data in terms of a much smaller number of items than do the individual variables. In the present study this approach was carried out using dietary items, total energy expenditure, body composition, biochemical and blood pressure baseline biomarkers. Including the twenty-nine variables shown in supplementary material (
Tables S12 and S13), 8 factors arouse. However, as aforementioned, this analysis presented certain limitations as the KMO value was under 0.6 (0.565), and because we had a smaller sample size for these variables for reasons explained in the limitation section at the end of this work. In addition, considering that this factor contributed to a low extent (7.7%) to the total variability, to improve this analysis, the factor related to energy expenditure (TEE, METs and average steps per day) was removed.
After removing the energy expenditure factor, twenty-six variables were reduced into seven factors explaining 81.5 % of the total variance (
Table 9). Out of the seven factors, three (1, 6 and 7) were composed of dietary variables accounting for 35.4 % of total data variability. These results are in line with a previous study [
77] using a similar statistical approach (PCA) carried out with dietary, body composition and biochemical variables. As in Garaulet et al. [
77], the main factor was composed of total lipid intake, as well as lipid composition (MUFA, SFA, PUFA), proteins and dietary cholesterol (the ‘‘Caloric and lipid factor’’;
Table 9). These results point out to energy dense foods, animal products and foods with high-lipid content as the main dietary components contributing to participants’ overweight/obesity. Moreover, this result agrees with dietary unbalance identified with the 24-hour recall dietary analysis, that showed high intake of lipids, proteins and cholesterol (
Table 2 and
Table 3). Although with the dietary analysis software used (DIAL) the source of protein (i.e. animal or plant) cannot be distinguished, considering that dietary cholesterol is only found in animal products [
78] and due to the strong correlation found between protein intake and dietary cholesterol, both corrected by EI (
rho = 0.509,
p < 0.001), it could be inferred that the main source of protein in the participants’ diet was of animal origin. High consumption of protein coming from plant-based foods (legumes, nuts, seeds) had been associated with better health outcomes [
79], whilst higher consumption of animal products, specifically red or processed meat, has been related to cardiovascular diseases, mainly due to their high content of SFA [
80]. As aforementioned, the subjects of this study exceeded the recommended intake of SFA and protein, while their dietary fibre intake was low, which also points to a higher consumption of animal-based products (
Table 3) and low consumption of plant-based protein that are also sources of fibre and (poly)phenols, related to better health outcomes [
81]. This idea is reinforced with the low contribution of the ‘‘Plant-based diet factor” (5%) to the total variance.
(Poly)phenol intake values in the present work (1073 mg/day,
Table 1), were similar to those described in the EPIC study in Mediterranean countries (1011 mg/day) [
22]. In previous studies, these compounds have shown anti-obesity properties explained by different mechanisms, such as modulating some neuro-hormones that play a role in satiety like neuropeptide Y, supressing lipogenesis or even modifying the microbiota. Therefore, a modification of dietary habits increasing the consumption of plant-based foods rich in phenolic compounds, including consumption of a (poly)phenol-rich coffee, could help to reduce the risk of developing obesity and/or treat comorbidities related to features of obesity/metabolic syndrome in certain subjects depending on baseline features [
82,
83]. This idea is based on a previous human study in which a blend of green/roasted coffee rich in (poly)phenols, was regularly consumed at a realistic rate (3 cups/day) by healthy and hypercholesterolemic subjects. The subjects with higher cardiovascular risk showed an improvement in cardiometabolic risk markers and abdominal adiposity, which were not observed in healthy subjects. Another important outcome of that study was the high interindividual variability in the biomarkers analysed [
23,
25,
84]. Not only did the percentage of responders and non-responders vary between the two study groups, but there was also a large variability in the extent of the response, with variations in the range of 1-115 units decrease in total cholesterol or TG as an example.
Even though the “Caloric and lipid” factor (EI, lipids and proteins) explained most variability (25 %), the “Adiposity factor” and “Cardiometabolic risk factor” had a considerable contribution to total variability in the PCA (16.9% and 13.2%, respectively;
Table 8). The relevance of the secondary factor related to adiposity (% body fat, visceral fat area, etc.) may be attributed to the adipose tissue being not only an energy reservoir but also a secretory organ of certain molecules that have endocrine, paracrine, and autocrine actions, that are involved in the regulation of body weight (leptin, adiponectin), in the local inflammation generated in obesity (tumour necrosis factor α, interleukin (IL)-6, and IL-1β), or in vascular function (angiotensin II and plasminogen activator inhibitor-1) [
85,
86]. The low-grade inflammation is closely related to insulin resistance and angiogenesis which would explain the importance of the next factor that accounts for more variability, the “Cardiovascular risk factor” (main loadings TG, VLDL, HDL). Accordingly, most participants had elevated abdominal and subcutaneous obesity measured by different indices (
Table 5 and
Table 6), elevated cardiometabolic risk attending to high total cholesterol values, and glycosylated haemoglobin (HbA1c) levels that indicated that most participants could be at risk of prediabetes. The fifth component was the “Blood pressure & abdominal fat component”, which accounted for 6.5% of the variability, showing that SBP, DBP and the waist/hip ratio were interconnected. These findings were in accordance with other studies showing a dose response relationship between higher values of waist to hip ratios and increased risk of hypertension [
87].
To sum up, an unbalanced ratio between energy intake and expenditure, with an inadequate dietary composition, high in lipids and proteins of animal origin, low in dietary fibre and bioactive compounds (such as (poly)phenols), might trigger body composition changes by elevating subcutaneous and visceral fat. These changes in adiposity may alter the serum lipid profile, leading to hypercholesterolemia, hypertriglyceridemia, insulin resistance and inflammation, thus connecting obesity, and especially abdominal obesity, with metabolic syndrome, T2D or cardiovascular disease [
86].