Detection of brown adipose tissue using infrared thermal imaging modality and changes of related biomarkers after low carbohydrate high fat diet

Abstract

In Malaysia, approximately 17, 18 and 30 percent are diabetic, obese and overweight respectively. A low carbohydrate high fat diet (LCHF) surfaced since the 1920s, has numerous clinical impacts and yet has not been used widely to combat obesity due to concerns about its safety, applicability and sustainability towards patients. Brown Adipose Tissue (BAT) is an endocrine organ which increases metabolism by generating non shivering thermogenesis (NST). Chronic exposure to ketones from LCHF is known to stimulate the BAT as proven in animal studies. Although, nuclear imaging is considered the gold standard for BAT quantification, the thermal imaging is a non-invasive yet cheap modality that is at par for clinical translation. The objective of this study is to determine whether LCHF increases the BAT heat dispersion area and its biomarkers more effectively than the unrestricted normal diet. This was a single-center, randomized, crossover trial of low LCHF versus unrestrictive normal (UN) diet. Each subject underwent one week of either LCHF or UN diet after randomization, followed by a week of washout period before completing the study with the opposite diet for one week. There were two dietary sequence of the study and four sampling points. The sampling included thermal imaging of the supraclavicular area, body composition and blood glucose and ketones. The primary outcome measure was the mean change in BAT thermal dispersion area and heat energy during using ANCOVA adjusted to the baselines. Secondary outcomes include, changes in body weight, BMI, body fat, visceral fat, fasting blood glucose, fasting blood ketone. Tertiary outcome was the correlation between the primary and secondary outcomes at both dietary periods. Fourteen subjects were recruited between June 2019 and October 2019. Twelve subjects completed the four points of the study and two subjects dropped out. None of the subjects reported any side effect of the LCHF diet. The primary outcome of this study was that no significant changes were seen in the BAT Thermal dispersion area and heat energy at both dietary periods and sequence. Secondary outcomes showed significant decrease in body weight in both dietary period and sequence (F(1,8)=15.775, and F(1,8)=7.210). There was also a significant decrease in BMI during first dietary period (F(1,8)=10.069). Elevation of ketones were only significant during the second dietary period (F(1,8) = 11.56). There were significant positive correlation between the BAT thermal properties and body weight, BMI, glucose and ketones during both dietary period. One week of LCHF diet did not increase both BAT heat dispersion area and heat energy. It was also not sufficient to reduce visceral fat, body fat and fasting blood glucose. Nevertheless, it lowered body weight, BMI and increased fasting blood ketones in the same timeframe.