In this proposal, the investigators challenge the assumption that following the physical activity guidelines implies benefit for ALL adults, and that if benefit is not achieved in response to first line therapy, it will be by simply exercising more. Thus, for improving cardiorespiratory fitness and cardiometabolic risk factors, unanswered questions include: 1) To what extent, regardless of increasing exercise intensity or amount, is exercise not associated with benefit? Demonstration of a resistance to benefit through exercise in a substantial number of adults would be a novel and important finding, would counter the assumptions of many if not most health care practitioners, and could have immediate and direct application in all health care settings. 2) To what extent will non-responders to first line therapy (150 min/wk) be required to increase exercise intensity or amount to achieve benefit? 3) To what extent will failure to improve CRF segregate (be associate with) with cardiometabolic risk factors? The investigators propose that adults who remain exercise resistant for improvement in CRF and cardiometabolic risk despite increasing amount or intensity are at high risk of metabolic disease and consequently, are candidates for alternative treatment strategies.

The trial has two objectives:

Primary objective: After 16 weeks of first line therapy (150 min/wk of MPA), does increasing exercise intensity or amount for 16 weeks improve cardiorespiratory fitness (CRF, VO2peak) deferentially depending on the CRF response at 16 weeks.

Secondary objective: Determine whether common cardiometabolic risk factors segregate/cluster with respect to variation in CRF to first line therapy in adults, and, whether clinically meaningful improvements in cardiometabolic risk factors segregate with improvement in CRF.

Inclusion Criteria:

• Sedentary lifestyle (planned physical activity for one day per week or less).
• Weight stable (± 2 kg) for 6 months prior to the beginning of the study.
• BMI between 20 and 40 kg/m2.

Exclusion Criteria:

• Physical impairment which would make the intervention very difficult or unsafe according to doctor's advice.
• Diabetes, current smokers.
• Plan to move from the area in next 8 months.

All data will be made available upon request.

Within 1 year of study completion.

Deidentified participant data collected during the trial will be available to external groups upon scientific review.