Decreased thermogenic response to food with intragastric vs. oral feeding

Diet induced thermogenesis, older and newer data with emphasis on obesity and diabetes mellitus - A narrative review

Obesity is a major public health problem with a prevalence increasing at an alarming rate worldwide. There is an urgent need for efficient approaches to weight management. Diet induced thermogenesis (DIT) is the process by which the body increases its energy expenditure in response to a meal. It is estimated to account for approximately 10 % of total energy expenditure and is considered a potentially modifiable component of energy expenditure. The palatability of food, meal's composition in macronutrients, the circadian rhythm and sleep, as well as individual's characteristics such as age, the presence of obesity or diabetes mellitus, and the proportion of physical activity are the main factors that affect DIT. However, studies examining DIT are mostly characterized by small sample size and the methodology varies considerably between studies. It seems that even today there is a lot of contradiction between the relative studies. Inspite of that, future research might lead to the modification of DIT in order to achieve some weight loss in obese people.

Water-induced thermogenesis and fat oxidation: a reassessment

Background/Objectives:

Drinking large amounts of water is often recommended for weight control. Whether water intake stimulates energy and fat metabolism is, however, controversial with some studies reporting that drinking half a litre or more of water increases resting energy expenditure (REE) by 10–30% and decreases respiratory quotient (RQ), whereas others report no significant changes in REE or RQ. The aim here was to reassess the concept of water-induced thermogenesis and fat oxidation in humans, with particular focus on interindividual variability in REE and RQ responses, comparison with a time-control Sham drink, and on the potential impact of gender, body composition and abdominal adiposity.

Subjects/Methods:

REE and RQ were measured in healthy young adults (n=27; body mass index range: 18.5–33.9 kg m⁻²), by ventilated hood indirect calorimetry for at least 30 min before and 130 min after ingesting 500 ml of purified (distilled) water at 21–22 °C or after Sham drinking, in a randomized cross-over design. Body composition and abdominal fat were assessed by bioimpedance techniques.

Results:

Drinking 500 ml of distilled water led to marginal increases in REE (<3% above baseline), independently of gender, but which were not significantly different from Sham drinking. RQ was found to fall after the water drink, independently of gender, but it also diminished to a similar extent in response to sham drinking. Interindividual variability in REE and RQ responses was not associated with body fatness, central adiposity or fat-free mass.

Conclusions:

This study conducted in young men and women varying widely in adiposity, comparing the ingestion of distilled water to Sham drinking, suggests that ingestion of purified water per se does not result in the stimulation of thermogenesis or fat oxidation.

Interaction between dietary fat and exercise on excess postexercise oxygen consumption

The objective of this study was to determine the effect of increased physical activity on subsequent sleeping energy expenditure (SEE) measured in a whole room calorimeter under differing levels of dietary fat. We hypothesized that increased physical activity would increase SEE. Six healthy young men participated in a randomized, single-blind, crossover study. Subjects repeated an 8-day protocol under four conditions separated by at least 7 days. During each condition, subjects consumed an isoenergetic diet consisting of 37% fat, 15% protein, and 48% carbohydrate for the first 4 days, and for the following 4 days SEE and energy balance were measured in a respiration chamber. The first chamber day served as a baseline measurement, and for the remaining 3 days diet and activity were randomly assigned as high-fat/exercise, high-fat/sedentary, low-fat/exercise, or low-fat/sedentary. Energy balance was not different between conditions. When the dietary fat was increased to 50%, SEE increased by 7.4% during exercise (P < 0.05) relative to being sedentary (baseline day), but SEE did not increase with exercise when fat was lowered to 20%. SEE did not change when dietary fat was manipulated under sedentary conditions. Physical activity causes an increase in SEE when dietary fat is high (50%) but not when dietary fat is low (20%). Dietary fat content influences the impact of postexercise-induced increases in SEE. This finding may help explain the conflicting data regarding the effect of exercise on energy expenditure.

The influence of oral water load on energy expenditure and sympatho-vagal balance in obese and normal weight women

INTRODUCTION

Oral water load may increase the energy expenditure (EE) by stimulation of sympathetic dependent thermogenesis. Thus, drinking of water may be helpful in weight reduction. The aim of the study is to assess the influence of water load on energy expenditure and sympathetic activity in obese and normal weight women.

MATERIAL AND METHODS

Forty-five women were included. Energy expenditure was measured twice, in the morning and after oral water load, by the indirect calorimetric method. The heart rate variability parameters low frequency (LF), high frequency (HF), LF/HF index, standard deviation of normal RR intervals (SDNN) and root mean square difference among successive RR normal intervals (rMSSD) were used for the indirect assessment of the sympatho-vagal balance.

RESULTS

Resting energy expenditure (REE) was significantly higher in obese than in normal weight women (1529 ±396 kcal/day vs. 1198 ±373 kcal/day; p = 0.02). In both study groups after water load EE increased significantly (by 20% and by 12%, corresponding to 8.6 kcal/h and 5.2 kcal/h respectively), while, LF/HF index increased simultaneously. The increase of energy expenditure (EE) did not exceed the energetic cost of water heating, from room to body temperature - 15 kcal/1000 ml. There was no correlation between changes of energy expenditure (EE) and heart rate variability (HRV) parameters.

CONCLUSIONS

The increase of EE induced by water load is mostly related to the heating of the consumed water to body temperature. The assessment of autonomic balance by means of standard HRV indices had been found insufficient for detection of actually operating mechanisms.

Subtyping obesity with microarrays: implications for the diagnosis and treatment of obesity

OBJECTIVE

Obese patients respond differently to weight loss interventions. No efficient diagnostic tool exists to separate obese patients into subtypes as a means to improve prediction of response to interventions. We aimed to separate obese subjects into distinct subgroups using microarray technology to identify gene expression-based subgroups to predict weight loss.

DESIGN

A total of 72 obese men and women without family history of diabetes were enrolled in the study; 52 were treated with ephedra and caffeine (E+C) and 20 with placebo for 8 weeks. Adipose and skeletal muscle tissue biopsies were performed at baseline. RNA sample pairs were labeled and hybridized to oligonucleotide microarrays. Quantile normalization and gene shaving were performed, and a clustering algorithm was then applied to cluster subjects based on their gene expression profile. Clusters were visualized using heat maps and related to weight changes.

RESULTS

Cluster analysis of gene expression data revealed two distinct subgroups of obesity and predicted weight loss in response to the treatment with E+C. One cluster ('red') decreased to 96.87+/-2.35% body weight, and the second cluster ('green') decreased to 95.59+/-2.75% body weight (P<0.05). 'Red' cluster had less visceral adipose tissue mass (2.77+/-1.08 vs 3.43+/-1.49 kg; P<0.05) and decreased size of the very large fat cells (1.45+/-0.61 vs 2.16+/-1.74 microl; P<0.05) compared to 'green' cluster. Gene expression for both skeletal muscle and adipose tissue was also different between clusters.

CONCLUSIONS

Our study provides the first evidence that the combined approach of gene expression profiling and cluster analysis can identify discrete subtypes of obesity, these subtypes have different physiological characteristics and respond differently to an adrenergic weight loss therapy. This brings us that into an era of personalized treatment in the obesity clinic.

Relationships between thermic effect of food, insulin resistance and autonomic nervous activity

BACKGROUND

The thermic effect of food (TEF) is higher in lean than in obese human subjects.

OBJECTIVE

Relationships between TEF and insulin resistance during meals, from the point of view of autonomic nervous activity, were evaluated.

METHODS

Autonomic nervous activity was evaluated in 20 young adults using the spectral analysis of heart rate variability from one hour before to two hours after a meal. Heart rate data were analyzed based on low frequency components (LF power, 0.04-0.15 Hz), high frequency components (HF power, 0.15-0.40 Hz), and LF/HF ratios. Energy expenditure and the TEF were measured 30 min after a meal. Homeostasis model of insulin resistance index (HOMA-IR) was also measured.

RESULTS

The LF/HF ratio was significantly increased 30 min after a meal (p<0.05). No correlation between LF power and HF power with TEF was found, but the LF/HF ratio was significantly and positively correlated with TEF (r=+0.56, p<0.05). Moreover, a significant negative correlation was found between the HOMA-IR and TEF (r=-0.601, p<0.05).

CONCLUSIONS

The findings suggest that a reduction in insulin sensitivity induces a poor response of sympathetic nervous activity in the postprandial phase and a reduction in postprandial energy expenditure.

Thermogenesis induced by osmotic stimulation of the intestines in the rat

Infusion of 5-20% glucose, 1.8-3.6% NaCl, 20% methylglucose, 20% fructose, or 5-10% solutions of various amino acids (10 ml x kg(-1)) into the duodenum induced dose-dependent thermogenesis in urethane-anaesthetized rats. In contrast, infusion of 0.9% NaCl, distilled water, or safflower oil had no effect on the metabolic rate. Infusion of 7.2% urea induced a small and transient increase in the metabolic rate. These results suggested that the thermogenesis was caused mainly by changes in osmolality rather than by a specific action of the different solute molecules. The respiratory exchange ratio increased after the infusion of glucose, fructose, glycine, or serine, did not change after the infusion of NaCl, methylglucose, safflower oil, or distilled water, and decreased after infusion of arginine. Therefore, there was no relationship between substrate utilization and the occurrence of thermogenesis. Intestinal infusion of 3.6% NaCl elevated the plasma osmolality, with a plateau increase of approximately 20 mosmol x kg(-1). However, intravenous infusion of the same amount of NaCl induced a significantly smaller thermogenic response, although it elevated the plasma osmolality with a time course and magnitude similar to those obtained after the intestinal infusion. Infusion of NaCl into the hepatic portal vein or the peritoneal cavity also produced a significantly small thermogenic response. These results suggested an intestinal or mesenteric location for osmoreceptors. To test for possible stimulation of intestinal osmoreceptors after intake of a normal meal, we measured the osmolality of the intestinal contents. The osmolality of the duodeno-jejunal contents was 600-800 mosmol kg-1, whereas the plasma osmolality was 306 +/- 1 mosmol x kg(-1), which suggests that the intestinal osmoreceptors are stimulated after meals and are involved in diet-induced thermogenesis.

Increased thermogenic response to food and fat oxidation in female athletes: relationship with VO(2 max)

The thermogenic response to food (TRF) and substrate oxidation were studied in 12 endurance-trained and 13 untrained female subjects. Energy expenditure and substrate oxidation were calculated by indirect calorimetry before and for 6 h after an oral test meal and after the same meal given intragastrically on a separate occasion. The TRF was calculated after the oral meal, the obligatory component after the intragastric meal (OTRF), and the facultative component from the difference between the two. VO(2 max) was measured on a treadmill and body composition by underwater weighing. The TRF and OTRF were significantly higher in trained than in untrained subjects: 223 +/- 63 vs. 185 +/- 50 kJ/6 h (P < 0.03) and 174 +/- 38 vs. 131 +/- 37 kJ/6 h (P < 0.01) for the TRF and OTRF in trained vs. untrained subjects, respectively. Multiple regression analysis showed that maximum O(2) consumption (VO(2 max)), but not percentage of body fat, was significantly related to OTRF (r =0.68, P < 0.01). Trained subjects had higher fatty acid oxidation than untrained subjects before (0.6 vs. 0.4 mg. kg(-1). min(-1), P < 0.05) and after the oral meal (13 +/- 6 vs. 8 +/- 4 g/6 h P < 0.05). These results demonstrate that 1) TRF is higher in trained than in untrained women; 2) this is due to a higher cost of nutrient digestion, absorption and storage; 3) the difference is related to higher VO(2 max); and 4) fatty acid oxidation is greater in trained women in both the postabsorptive and postprandial states. These observations suggest that endurance training induces metabolic changes that favor leanness.