Background:
Ketogenic diets are high fat and low carbohydrate or very low carbohydrate diets, which render high production of ketones upon consumption known as nutritional ketosis (NK). Ketosis is also produced during fasting periods, which is known as fasting ketosis (FK). Recently, the combinations of NK and FK, as well as NK alone, have been used as resources for weight loss management and treatment of epilepsy.

Methods:
A crossover study design was applied to 11 healthy individuals, who maintained moderately sedentary lifestyle, and consumed three types of diet randomly assigned over a three-week period. All participants completed the diets in a randomized and counterbalanced fashion. Each weekly diet protocol included three phases: Phase 1 - A mixed diet with ratio of fat: (carbohydrate + protein) by mass of 0.18 or the equivalence of 29% energy from fat from Day 1 to Day 5. Phase 2- A mixed or a high-fat diet with ratio of fat: (carbohydrate + protein) by mass of approximately 0.18, 1.63, or 3.80 on Day 6 or the equivalence of 29%, 79%, or 90% energy from fat, respectively. Phase 3 - A fasting diet with no calorie intake on Day 7. Caloric intake from diets on Day 1 to Day 6 was equal to each individual’s energy expenditure. On Day 7, ketone buildup from FK was measured.

Results:
A statistically significant effect of Phase 2 (Day 6) diet was found on FK of Day 7, as indicated by repeated analysis of variance (ANOVA), F(2,20) = 6.73, p < 0.0058. Using a Fisher LDS pair-wise comparison, higher significant levels of acetone buildup were found for diets with 79% fat content and 90% fat content vs. 29% fat content (with p = 0.00159**, and 0.04435**, respectively), with no significant difference between diets with 79% fat content and 90% fat content. In addition, independent of the diet, a significantly higher ketone buildup capability of subjects with higher resting energy expenditure (R[superscript 2] = 0.92), and lower body mass index (R[superscript 2] = 0.71) was observed during FK.

Energy Expenditure (EE) (kcal/day) is a key parameter used to guide obesity treatment, and it is often measured from CO2 production, VCO2 (mL/min), and/or O2 consumption, VO2 (mL/min) through the principles of indirect calorimetry. Current EE measurement technologies are limited due to the requirement of wearable facial accessories, which can introduce errors as measurements are not taken under free-living conditions. A novel contactless system, the SmartPad, which measures EE via VCO2 from a room’s ambient CO2 concentration transients was evaluated. First, SmartPad accuracy was validated by comparing the SmartPad’s EE and VCO2 measurements with the measurements of a reference instrument, the MGC Ultima CPXTM, in a cross-sectional study consisting of 20 subjects. A high correlation between the SmartPad’s EE and VCO2 measurements and the MGC Ultima CPX’s EE and VCO2 measurements was found, and the Bland-Altman plots contained a low mean bias for EE and VCO2 measurements. Thus, the SmartPad was validated as being accurate for VCO2 and EE measurements. Next, resting EE (REE) and exercise VCO2 measurements were recorded using the SmartPad and the MGC Ultima CPXTM at different operating CO2 threshold ranges to investigate the influence of measurement duration on system accuracy in an effort to optimize the SmartPad system. The SmartPad displayed 90% accuracy (±1 SD) for 14–19 min of REE measurement and for 4.8–7.0 min of exercise, using a known room’s air exchange rate. Additionally, the SmartPad was validated by accurately measuring subjects’ REE across a wide range of body mass indexes (BMI = 18.8 to 31.4 kg/m^2) with REEs ranging from ~1200 to ~3000 kcal/day. Lastly, the SmartPad has been used to assess the physical fitness of subjects via the “Contactless Thermodynamic Efficiency Test” (CTET).

Realtime understanding of one’s complete metabolic state is crucial to controlling weight and managing chronic illnesses, such as diabetes. This project represents the development of a novel breath acetone sensor within the Biodesign Institute’s Center for Bioelectronics and Biosensors. The purpose is to determine if a sensor can be manufactured with the capacity to measure breath acetone concentrations typical of various levels of metabolic activity. For this purpose, a solution that selectively interacts with acetone was embedded in a sensor cartridge that is permeable to volatile organic compounds. After 30 minutes of exposure to a range of acetone concentrations, a color change response was observed in the sensors. Requiring only exposure to a breath, these novel sensor configurations may offer non-trivial improvements to clinical and at-home measurement of lipid metabolic rate.

Using supported ionic-liquid membrane (SILM)-inspired methodologies, we have synthesized, characterized, and developed a humidity sensor by coating a liquid composite material onto a hygroscopic, porous substrate. Similar to pH paper, the sensor responds to the environment’s relative humidity and changes color accordingly. The humidity indicator is prepared by casting a few microliters of low-toxicity reagents on a nontoxic substrate. The sensing material is a newly synthesized liquid composite that comprises a hygroscopic medium for environmental humidity capture and a color indicator that translates the humidity level into a distinct color change. Sodium borohydride was used to form a liquid composite medium, and DenimBlu30 dye was used as a redox indicator. The liquid composite medium provides a hygroscopic response to the relative humidity, and DenimBlu30 translates the chemical changes into a visual change from yellow to blue. The borate–redox dye-based humidity sensor was prepared, and then Fourier transform infrared spectroscopy, differential scanning calorimetry, and image analysis methods were used to characterize the chemical composition, optimize synthesis, and gain insight into the sensor reactivity. Test results indicated that this new sensing material can detect relative humidity in the range of 5–100% in an irreversible manner with good reproducibility and high accuracy. The sensor is a low-cost, highly sensitive, easy-to-use humidity indicator. More importantly, it can be easily packaged with products to monitor humidity levels in pharmaceutical and food packaging.

A novel portable wireless volatile organic compound (VOC) monitoring device with disposable sensors is presented. The device is miniaturized, light, easy-to-use, and cost-effective. Different field tests have been carried out to identify the operational, analytical, and functional performance of the device and its sensors. The device was compared to a commercial photo-ionization detector, gas chromatography-mass spectrometry, and carbon monoxide detector. In addition, environmental operational conditions, such as barometric change, temperature change and wind conditions were also tested to evaluate the device performance. The multiple comparisons and tests indicate that the proposed VOC device is adequate to characterize personal exposure in many real-world scenarios and is applicable for personal daily use.