Postprandial metabolic response depends on the meals’ components and can be different in normal weight and obese people. However, there are some discrepancies between various reports. The aim of this study was to determine the metabolic response after intake of standardised meals with various fat and carbohydrate contents and to determine the differences among normal weight and overweight/obese individuals. The study group comprised 46 healthy men. The participants were divided into two groups and study was carried out using a crossover method. Group I received high- and normal-carbohydrate meals, whereas group II received high-carbohydrate and high-fat meals. Glucose, insulin, triglyceride, and free fatty acids levels were measured at fasting state and at 30, 60, 120, 180, and 240 minutes after meal intake. Despite the lack of differences in glucose levels, insulin levels were higher among overweight/obese individuals after each meal. TG and FFA levels were higher after normal-carbohydrate and high-fat meals. Moreover, in overweight/obese young men after high-fat meal intake postprandial hypertriglyceridemia was observed, even if meals contained predominantly unsaturated fatty acids, and fasting triglycerides levels were in normal range. The conducted study showed that postprandial metabolic response depends not only on the meal macronutrient content but also on the current body mass index (BMI).
Obesity is a chronic metabolic disease and a growing medical issue with a global reach. In the last 30 years, a dramatic increase in number of people suffering from obesity has been observed. The prognosis for the future is alarming, as it is believed that, with current trends, over a billion of people will have been obese by the year 2030, and another 2 billion will have been overweight [
The aim of this study was to evaluate the metabolic changes after intake of meals with various fat and carbohydrate contents, using a crossover method, and to analyse the differences between postprandial metabolic responses among normal weight and overweight/obese healthy men. It was expected to discover early postprandial metabolic disturbances in young overweight/obese men in postprandial state, even if the baseline results were in normal range.
46 men participated in the study: 23 with normal weight (NW) and 23 were overweight/obese (OO) in the age range of 21–58 years. The study was conducted according to the guidelines laid down in the Declaration of Helsinki and all procedures involving patients were approved by the local Ethics Committee of the Medical University of Bialystok (Poland) and a written informed consent was obtained from all participants. The participants of the study did not suffer from any glucose metabolism disorders, endocrine disorders, renal or liver failure, and digestive system diseases, did not undergo any gastroenterological and bariatric surgeries or procedures, and did not suffer from any other diseases which could influence the results. People who had received pharmacological treatment or had used any other products with undocumented or unknown influence on metabolism were excluded from the study. Taking into consideration the fact that the levels of some factors can be characterised by sexual dimorphism and its analysis was not the aim of the study, only male participants were selected for the study group, in order to obtain reliable results.
Based on BMI, the participants were divided into two groups: men with normal weight (NW, BMI < 25.0 kg/m2) and men that were overweight/obese (OO, BMI ≥ 25.0 kg/m2). Subsequently, the participants were randomly divided (randomisation using sampling without replacement) into two experimental groups (the study design is presented in Figure
The characteristic of study groups.
Group I | NW |
OO |
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Age, years | 33 ± 2 | 40 ± 2 | <0.02 |
BMI, kg/m2 | 23.8 ± 0.5 | 31.4 ± 1.5 | <0.001 |
Body fat content, % | 17.9 ± 1.0 | 28.6 ± 1.7 | <0.0001 |
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Group II | NW |
OO |
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Age, years | 33 ± 3 | 36 ± 3 | >0.05 |
BMI, kg/m2 | 23.9 ± 0.2 | 33.7 ± 2.2 | <0.00001 |
Body fat content, % | 18.6 ± 1.5 | 31.9 ± 2.7 | <0.001 |
Data are presented as a mean value ± SE.
Study design. NW: normal weight; OO: overweight/obese.
Group I (11 NW men and 12 OO men) received a high-carbohydrate (HC) meal (450 kcal), 89% of energy coming from carbohydrates, 11% coming from protein, and 0% coming from fat (Nutridrink Fat Free, Nutricia, Poland), and, then, after a period of 1-2 weeks received a meal with normal-carbohydrate (NC) content (450 kcal), 45% of energy coming from carbohydrates, 30% coming from protein, and 25% coming from fat: 12,4% SFA, 59,0% monounsaturated fatty acids (MUFA), 28.7% polyunsaturated fatty acids (PUFA), and n-6/n3 ratio 5,11 (Cubitan, Nutricia, Poland).
Group II (12 NW men and 11 OO men) received a HC (fat-free) meal (450 kcal), 89% of its energy coming from carbohydrates, 11% coming from protein, and 0% coming from fat (Nutridrink Fat Free, Nutricia, Poland), and, then, after a period of 1-2 weeks received a high-fat (HF) meal (450 kcal), 4% of energy coming from carbohydrates, 0% coming from protein, and 96% coming from fat: 10.7% SFA, 60.7% monounsaturated fatty acids (MUFA), 28.6% polyunsaturated fatty acids (PUFA), and n-6/n3 ratio 5,02 (Calogen, Nutricia, Poland).
The participants were asked not to change their diet and daily physical activities during the study.
The participants were arriving at the lab at 08:00–08:30 in the morning, in the fasting state, with at least 12 hours since their last meal. The following procedures were carried out: height and weight measurements and body fat content measurement (using the bioimpedance method, InBody 220 Biospace, Korea). A peripheral venous catheter was placed in the elbow crook and venous blood was drawn in order to determine fasting blood glucose and insulin and free fatty acids (FFAs) and triglyceride (TG) levels. The participants then received a randomly selected meal (at room temperature) and were advised to consume it within 10 minutes. 30, 60, 120, 180, and 240 minutes after meal intake the venous blood was drawn in order to measure the above-mentioned factors levels again.
The specimen was drawn and prepared for testing in accordance with the recommendations provided by the laboratory kit producers. The assay of particular levels was carried out immediately after drawing the specimen, while the remaining ones were determined after the specimen was obtained for the whole period of tests. The specimen was stored in accordance with the recommendations of the producers until it was tested, at temperature of −20°C/−80°C. The particular factors levels were determined using the following methods: glucose-hexokinase enzymatic colorimetric assay (Cobas c111, Roche Diagnostics Ltd., Switzerland), insulin-immunoradiometric assay (Insulin, IRMA, DiaSource, Belgium; Wallac Wizard 1470 Automatic Gamma Counter, PerkinElmer, Life Science, Turku, Finland), TG-enzymatic colorimetric assay (Cobas c111, Roche Diagnostics Ltd., Switzerland), FFAs-enzymatic assay (FFA ELISA, Zen-Bio, Czech Republic;
In order to obtain the general characteristics of the data, arithmetic mean and standard error of the mean were calculated for all numerical features, which were treated as dependent variables in subsequent steps of the analysis. The aim of the study was to check whether there is a statistically significant postprandial metabolic response depending on meals’ components. There were two main null hypotheses stated: (1) different types of meals (differentiated by main component of the meal) have no influence on postprandial metabolic response in normal weight and overweight/obese patients (analyzed separately); (2) there is no difference in postprandial metabolic response to a particular meal in normal weight and overweight/obese patients. The first hypothesis (1) was verified for two pairs of meals: HC versus NC and HC versus HF for normal weight and overweight/obese subjects. Since both meals were given to the same patients, tests for dependent variables were used: either one-way ANOVA or Wilcoxon signed-rank test (both for paired samples)—depending on fulfilling of the condition of the normality of the variables’ distribution. The second hypothesis (2) was verified for each type of meal: HC, NC, and HF in order to check whether there are significant differences in postprandial metabolic response between normal weight and overweight/obese subjects. One-way ANOVA or Wilcoxon rank-sum test (both for unpaired samples)—depending on fulfilling of the condition of the normality of the variables’ distribution—and the homogeneity of variances were used to test the stated hypothesis. To address the issue of multiple hypothesis testing, false discovery rate
The blood glucose levels were significantly higher after the HC meal intake than after NC meal at 30 and 60 minutes in OO men and also at 120 minutes in NW individuals (Figure
Blood glucose levels (mg/dL) in normal weight (NW) and overweight/obese (OO) men in fasting state (time 0 min) and after (time 30–240 min): (a) high-carbohydrate (HC, black circle) and normal-carbohydrate (NC, white square) meal intake. (b) High-carbohydrate (HC, black circle) and high-fat (HF, white triangle) meal intake. Data are presented as mean value ± SE. Comparison between different meals in NW or OO men:
The blood glucose levels were significantly higher after HC meal in comparison to HF meal as well, both in NW and in OO men (Figure
At fasting and postprandial state (Figures
The insulin levels were significantly higher after HC meal in comparison to NC meal, both in NW and in OO men (Figure
Insulin levels (IU/mL) in normal weight (NW) and overweight/obese (OO) men in fasting state (time 0 min) and after (time 30–240 min): (a) high-carbohydrate (HC, black circle) and normal-carbohydrate (NC, white square) meal intake. (b) High-carbohydrate (HC, black circle) and high-fat (HF, white triangle) meal intake. Data are presented as a mean value ± SE. Comparison between different meals in NW or OO men:
The insulin levels in NW and OO men were also significantly higher after HC meal intake, in comparison to HF meal (Figure
While comparing the insulin levels between NW and OO men, the OO men from group I had significantly higher insulin levels both at fasting state and after HC and NC meals intake (Figure
In the OO men the TG levels were significantly higher after NC meal at 120, 180, and 240 minutes, in comparison to the levels after HC meal (Figure
Triglycerides levels (mg/dL) in normal weight (NW) and overweight/obese (OO) men in fasting state (time 0 min) and after (time 30–240 min): (a) high-carbohydrate (HC, black circle) and normal-carbohydrate (NC, white square) meal intake. (b) High-carbohydrate (HC, black circle) and high-fat (HF, white triangle) meal intake. Data are presented as a mean value ± SE. Comparison between different meals in NW or OO men:
When comparing the TG levels after HC meal with the TG levels after HF meal intake, from 120 to 240 minutes in NW and from 180 to 240 minutes in OO men the TG levels were significantly higher after HF meal intake (Figure
No differences between NW and OO men (Figures
Both, in NW and in OO men, the FFAs levels were significantly higher from 120 to 240 minutes after NC meal intake, in comparison to the levels after HC meal (Figure
Free fatty acids (FFAs) levels (
The FFAs levels were similar among NW and OO men, both at fasting and after HC and NC meals intake (Figures
The study confirmed that metabolic response depends on the components of a meal and on the current body energy balance. Moreover, after HF meal intake postprandial hypertriglyceridemia was noted in OO men, even if fasting TG levels were within the normal range and the meal contained predominantly unsaturated fatty acids. It is worth noticing that the investigated study groups comprised healthy young men, and, in spite of this, we observed very early disturbances in postprandial metabolic response, which in long-term can lead to development or progress of metabolic disorders such as obesity, hypertriglyceridemia, metabolic syndrome, and type 2 diabetes.
The highest glucose levels after HC meal, observed in NW men and in OO men, were not surprising and are consistent with the results obtained by other researchers [
The study showed that glucose levels in general were not different for NW and OO people, both at fasting and after each of the meals. Other researchers also did not observe any significant differences in glucose levels between people with normal weight and those with obesity after high-carbohydrate and high-fat meals intake [
The insulin levels, both in NW men and in OO men, were significantly higher after HC meal intake than after NC or HF meal. The increased secretion of insulin was undoubtedly a result of higher glucose levels after high-carbohydrate meal, which was also confirmed in studies carried out by other authors [
Despite the lack of significant differences in glucose levels, the insulin levels were significantly different both in fasting and in postprandial states. OO men had significantly higher fasting insulin levels after HC, NC, and HF meals intake (in comparison to NW men). Other researchers also observed higher insulin levels, at fasting state and after a meal intake in people with obesity, also with a lack of significant differences in glucose levels [
When comparing meals with different composition, we have noticed that in OO men, after NC meal intake, the TG levels were significantly higher in comparison to the levels after HC meal intake. Also among OO men the AUC for TG levels was significantly higher after NC meal, whereas among NW men the AUCs for TG levels after HC and NC meal did not differ significantly. The TG levels were also significantly higher after HF meal in comparison to HC meal, both in NW and in OO men. Other researchers also proved that the high-fat meal intake is related to the increase of TG levels, where the maximum values were obtained 4 hours after ingesting the meal [
Also the high FFAs levels are responsible for elevated endothelial activation markers, vascular endothelial cell inflammation, and increased prothrombotic activity markers, which can cause vascular and atherosclerotic anomalies resulting in circulatory system diseases [
The conducted analyses did not show any significant differences in fasting FFAs levels between NW and OO people, and the AUCs for FFAs levels after HC and NC meals were the same for NW and OO people as well. However, 60 minutes after HF meal intake higher FFAs levels were observed among OO people in comparison to NW men and remained significantly higher until 180 minutes of the test. Also the AUC of FFAs levels in postprandial state after a high-fat meal intake was significantly higher in OO than in NW men. Imbeault et al. [
The differences in postprandial metabolic effects, especially in lipids response, probably can be explained by the lower numbers of lipoprotein particles of hepatic origin that compete with chylomicrons for lipolysis [
Moreover, the postprandial response can be dependent also on the other, for example, genetic factors, which we have observed in one of our previous studies [
In summary, the conducted study confirmed that postprandial metabolic response depends on the components of a meal and moreover it is different among NW and OO people.
The highest blood glucose levels were observed after HC meal intake; however the levels were the same for NW and OO people. Insulin levels were also the highest after HC meal intake, and, despite the lack of significant differences in blood glucose levels, higher insulin levels were observed in OO people, in comparison to the NW group. Triglyceride and FFAs levels were higher after NC and HF meals intake. In OO people, postprandial hypertriglyceridemia was observed after HF meal intake, even if it contained mostly unsaturated fatty acids. Further investigations on the effect of MUFA on the CHD risk are undoubtedly warranted. Nevertheless, our findings showed that metabolic response in OO people to high-fat meals, even if rich in unsaturated fatty acids, caused postprandial hypertriglyceridemia and should be avoided in diet. Even if the study sample size was quite small and our results need to be confirmed, for example, by increasing the sizes of study groups, the obtained results have crucial significance in a period of obesity plague and of the omnipresent trends of diets with modified amount of macronutrients, including high-fat diets.
The authors declare that they have no conflict of interests.
Edyta Adamska, Lucyna Ostrowska, Adam Krętowski, and Maria Górska conceived the idea for the study, contributed to the design of the research, interpreted the results, and wrote the paper. Edyta Adamska and Magdalena Waszczeniuk were involved in the data collection. Joanna Gościk performed statistical analyses and contributed to the discussion. Maria Górska and Adam Krętowski coordinated funding for the project.
The study was supported by Medical University of Bialystok, Poland, and by funding from The Leading National Research Centre in Bialystok, Poland.