Effects of Physical Inactivity on Insulin Sensitivity, Appetite, Energy Balance, and Cardiovascular Responses in Humans.

Short-term Effects of Physical Inactivity on Insulin Sensitivity, Appetite, Energy Balance, and Cardiovascular Responses in Healthy Humans.

Physical inactivity is a significant predictor of major non-communicable diseases such as type 2 diabetes (7%), cardiovascular disease (6%), musculoskeletal disorders and some cancers, and has been proposed to be the 4th leading cause of death worldwide. Reduced physical activity leads to an impaired function of the hormone insulin and increased adiposity. Thus, the elimination of physical inactivity would remove between 6% and 10% of the major non-communicable diseases and increase life expectancy. The aim of the study is to investigate the effects of a short-term (2-day) period of reduced physical activity, with and without a proportional decrease in energy intake, on the action of insulin to regulate blood sugar fluctuations, appetite, and cardiovascular parameters (heart rate, cardiac output, stroke volume, blood flow, arterial blood pressure, peripheral vascular resistance) in response to food ingestion.

Inclusion Criteria:

• Non-smoking
• Males and females
• Age (18-35 years old)
• Body mass index (BMI) of 18-27 kg/m2
• Waist circumference <94cm for males and <80cm for females
• Ability to give informed consent

Exclusion Criteria:

• Smoking
• Any metabolic (e.g. diabetes), endocrine (e.g. hyperthyroidism) or cardiovascular (e.g. heart or blood) abnormalities including hypertension or heart failure
• Clinically significant abnormalities on screening including ECG abnormalities
• Taking routine medication that may alter cardiovascular function and blood flow (e.g. blood pressure-lowering drugs or drugs that cause hypertension)
• Well trained individuals with PAL>2.00; on an energy-restricted diet or seeking to lose weight
• High alcohol consumption (<3-4 units/d for men; <2-3 units/d for women)
• Females who are pregnant or lactating; self-reported allergy, intolerance or strong dislike of foods or drinks to be offered for the test breakfast, pasta meal or during the intervention period
• Beck Depression Inventory score >10 and Eating Attitudes Test (EAT-26) score >20 as self-reported markers of symptoms and concerns characteristic of depression and eating disorders, respectively.