Omega-3 Fatty Acids as Regulators of Brown Adipose Tissue During Cold Exposure

Core body temperature will be continuously measured by a rectal probe

Metabolic rate will be measured via indirect calorimetry (i.e., via the analysis of expired gases and ventilation).

Surface mechanomyography will be assessed by three triaxial accelerometers adhered to the skin using adhesive tape on the chest, upper back, and thigh will be used to assess shivering

The MMDT [28,29,30] consists of a 60-hole, thin board with red and black blocks (3.7cm) and is comprised of the turning test and the placing test. During the turning test will be modified to only use the dominant hand. During this task, the participant takes a block from the top right corner with their dominant and places it in the hole with their dominant hand. During the placing test, the participant takes one at a time in their dominant hand and places the black in the whole on the board. Scoring of this test is the time it takes to complete each test.

Thermal perceptions will be assessed using Likert scales for thermal discomfort and thermal sensation. Thermal perceptions will be assessed using Likert scales for thermal discomfort and thermal sensation. Participants will complete Likert scales to assess their thermal comfort (1 = comfortable, 4 = very uncomfortable) and thermal sensation (1 = cold, 4 = neutral, 7 = hot).

A series of small tubes will be placed on the back of the participant's neck. The participants will control the temperature of the water perfusing these tubes by turning a valve. This will allow for the voluntary control of neck temperatures from 20-35 degrees Celsius. Participants will be instructed to control the temperature of the water bath so that their neck will always be thermally comfortable

An infrared thermography camera will be used to measure skin temperature in the supraclavicular (i.e., collar bone) region. This provides a non-invasive estimate of brown adipose tissue activation

The environmental chamber set to 29 degrees Celsius (C; 84 degrees Fahrenheit, F) at the beginning of the experimental visit. While in the chamber, participants will be instructed to be sedentary. The chamber will then be cooled at a rate of 1 deg C per 5 minutes until 4 deg C (39.2 deg F) is reached (~125 minutes) with a wind speed of 4.5 m/s. Once 4 deg C air temperature is reached, participants will remain in the chamber for an additional 30 minutes or until the participant can no longer tolerate the cold or if rectal temperature falls below 35.5 deg C (95.9 deg F).

Participants will be asked to record all food, beverages and supplements consumed during a 24-hour period pre-supplementation, and every 2 weeks during the supplementation period for a total of ~7 dietary recalls to ensure that dietary habits do not change during the 12 week supplementation period.

Wireless temperature sensors (iButtons, Maxim Inc.) will be attached to 12 sites on the body (forehead, calf, thigh, foot, quadriceps, hamstring, chest, abdomen, upper back, lower back, forearm, and hand) using adhesive tape to measure skin temperature.

The NHPT, a manual dexterity test, consists of 9 holes (10mm diameter, 15mm depth) separated by 32mm, and 9 pegs (7mm diameter, 32mm length). During the test, participants will be instructed to take the pegs from a container one by one and place them into the holes on the board as quickly as possible, with their dominant hand. Scoring of this test is the time it takes to complete each test.

Digital blood pressure cuff will evaluate resting blood pressure

Hydration status via urine specific gravity (USG) by a handheld refractometer will be utilized and USG < 1.020 will indicate euhydration. For females of child-bearing potential, a small sample of urine will be used for a urine pregnancy test.

Participants will be connected to a 3-lead electrocardiogram (ECG).

Digital blood pressure cuff will evaluate resting pulse rate

A total-body Dual Energy X-Ray Absorptiometry (DEXA) procedure will be used to assess bone mineral density (g. cm-3) at various body segments (e.g., total body, trunk, hip, leg).

A total-body Dual Energy X-Ray Absorptiometry (DEXA) procedure will be used to assess lean muscle mass (kilograms or pounds) at various body segments (e.g., total body, trunk, hip, leg).

A total-body Dual Energy X-Ray Absorptiometry (DEXA) procedure will be used to assess fat mass (kilograms or pounds) at various body segments (e.g., total body, trunk, hip, leg).

A total-body Dual Energy X-Ray Absorptiometry (DEXA) procedure will be used to assess body fat percentage (%) at various body segments (e.g., total body, trunk, hip, leg).