The current focus of the Obesity and Diabetes Clinical Research Section is on examining the determinants of energy intake and energy expenditure, understanding the psychosocial underpinnings of appetitive behaviors, and predictors of dietary intake patterns. Our research section utilizes a number of state-of-the-art approaches and methodologies, including: (1) longitudinal, natural histories of weight change and diabetes risk, (2) clinical inpatient studies that use whole room Indirect calorimeters to measure energy expenditure, (3) ad libitum vending machine paradigms to facilitate in ad libitum feeding studies, (4) biomarker and genetic assays to measure hormonal and genetic mechanisms of metabolism.
Ad libitum vend paradigm
Our inpatient clinical studies use an electronic vending machine paradigm to measure ad libitum food consumption. Participants are assigned a vending machine that is stocked based on their responses to a food preference questionnaire. Their food choices, macronutrient content and amount eaten are tracked through a barcode system and data is processed by the metabolic kitchen staff. This vend paradigm has been demonstrated to have high intra-individual reliability (daily energy intake ICC = .90; Venti et al., 2009, Am J Clin Nutr, 91, 343–348)
The impact of food insecurity status on energy intake
Stinson and colleagues (Obesity, 26, 2018, 1841-1848) found that individuals with food insecurity consumed significantly greater energy intake during an ad libitum vend paradigm, including more fat and carbohydrates, and had greater maladaptive eating behaviors compared to food secure individuals.
Inverse association between peak diameter of thigh adipocytes and energy intake
Basolo and colleagues (Obesity, 2019, 28, 1129-1140) examined the associations between fat cell size and daily energy intake during ad libitum food consumption. In women, there was an inverse association between peak diameter of thigh adipocyctes and daily energy intake (adjusted for age, race, fat mass, and fat-free mass). This suggest that fat distribution in women’s thighs may be metabolically protective.
Carbon and nitrogen isotope ratios as determinants of dietary content
Votruba and colleagues (Am J Clin Nutr, 2019, 110, 1306–1315) examined whether isotope ratios (measured in blood and hair) are stable biomarkers of dietary content. Results demonstrated that level of nitrogen isotope ratios were greater in meat diets, particularly fish diets. Conversely, levels of carbon isotope ratios were greater in diets with characterized by a greater proportion of meat and sugar-sweetened beverages. This suggests that these biomarkers may be important in discriminating between diets that vary in content.
24h eucaloric energy expenditure and one-year weight regain following caloric restriction
In healthy individuals with obesity, Hollstein and colleagues (Int J Obes, 2021, https://doi.org/10.1038/s41366-021-00748-y
) found that higher eucaloric 24h energy expenditure predicted increased weight regain and greater fat and fat free mass at 1 year follow up after a 12 week caloric restriction intervention. Results suggest that metabolic efficiency during eucaloric conditions may inform those at risk for greater weight regain following weight loss.
Transcranial direct current stimulation (tDCS) and Obesity
We are currently investigating the impact of tDCS – a noninvasive procedure used to modulate brain activity - on eating behavior and weight. Previous research from our lab has established that compared to lean, individuals with obesity have lesser brain activation in the in the left dorsolateral prefrontal cortex (DLPFC), a brain region that regulates inhibition and control. In our prior studies of tDCS, Gluck et al [Obesity 2015; 23: 2149-56] observed greater % weight loss (P = 0.009) in participants during anodal versus cathodal tDCS. Heinitz and colleagues [Am J Clin Nutr 2017;106:1347–57] found decreased snack food intake and reduced hunger ratings after 5 weeks of anodal (active) compared to sham (control group) tDCS. Our current study willextend these findings by examining, over 9-weeks, the effects of repeated anodal vs. sham tDCS to the left DLPFC on food intake, satiety and weight. In addition, participants will undergo fMRI at the beginning and end of the study as a tool for identifying the mechanism of action and confirmation of target engagement.