Exercise to reduce body fat and metabolic risk with Dr. Robert Ross

In the Masters in Exercise podcast, Dr. Robert Ross, a kinesiology professor at Queen's University, discusses his research on lifestyle interventions for managing obesity and cardiometabolic risks. He highlights the limitations of using BMI alone to assess health risks, emphasizing the significance of measuring waist circumference due to the dangers of visceral fat. Dr. Ross explains that while exercise can reduce adiposity and improve insulin sensitivity, the effectiveness varies with exercise type and intensity. He advocates for a holistic approach, integrating exercise with diet and lifestyle changes, as outlined in Canada's 24-hour movement guidelines, to achieve sustainable health benefits.

• The phenotype of obesity is crucial in assessing health risks, with the abdominal obese phenotype being a strong marker of morbidity and mortality.
• Abdominal obesity can be measured by waist circumference or waist-to-hip ratio, and is a significant predictor of health risks.
• Radiographic imaging technologies like CT and MRI have allowed the differentiation between subcutaneous fat and visceral adipose tissue.
• Visceral adipose tissue, although a small proportion of total adiposity, is a principal target for obesity-related risk management due to its association with cardiometabolic risks.

"The phenotype of obesity matters. We have this abdominal obese phenotype, or the apple or the Android phenotype, and then we have the lower body or pear gynoid phenotype. Those two phenotypes are important simply because they identify different levels of risk."

• Abdominal obesity is more indicative of health risks compared to lower body obesity.

"Visceral adipose tissue conveys the greatest health risk. Even though it's a relatively small proportion of total adiposity, it is a principal target for strategies designed to manage obesity-related risk."

• Visceral fat is a significant health risk and a primary target for managing obesity-related risks.

"Visceral adipose tissue could cause insulin resistance because of its association with inflammatory cytokines is probably more the leading theory."

• Visceral fat's link to insulin resistance and inflammation is a key area of research in understanding its health risks.

• BMI alone is insufficient for assessing cardiometabolic risk; waist circumference provides additional valuable information.
• In some countries, BMI plateaus while waist circumference continues to rise, possibly due to aging demographics and changes in body composition.
• Sarcopenic obesity, characterized by increased abdominal fat and decreased muscle mass, is a growing concern, particularly in older populations.

"The combination of BMI and waist circumference identifies risk of morbidity and mortality greater, better than either anthropometric measure alone."

• Using both BMI and waist circumference provides a more comprehensive risk assessment.

"We see this routinely that what we call it tends to be called sarcopenic obesity is the term we use now to sort of describe that phenotype."

• Sarcopenic obesity is a recognized phenomenon associated with aging, involving increased abdominal fat and decreased muscle mass.

• Exercise can lead to reductions in both total and regional body fat, including abdominal fat.
• The reduction in fat due to exercise can be measured in absolute terms (kilograms) or relative terms (percentage), with relative reductions often more pronounced in visceral fat.
• Exercise-induced negative energy balance results in fat loss across all depots, not just abdominal fat.

"The good news is this, we're reducing adiposity everywhere, right? We do it everywhere."

• Exercise reduces fat throughout the body, not just in specific areas.

"In response to negative energy balance, whether you induce it through a restriction of caloric intake or you don't restrict caloric intake, you just increase energy expenditure. You are going to reduce adiposity in all depots."

• Both caloric restriction and increased energy expenditure through exercise lead to overall fat reduction.

• The discussion centers around the integrative approach combining exercise, diet, sleep, and reduction of sedentary time.
• The focus is on managing obesity, reducing adiposity, maintaining muscle mass, and reducing risk factors for chronic diseases.
• Exercise combined with a balanced diet without caloric restriction can reduce adiposity and improve insulin sensitivity.
• The challenge is sustaining weight loss rather than achieving it initially.

"Exercise combined with a balanced, healthful diet in the absence of caloric restriction, is associated with reductions in total adiposity, abdominal adiposity, visceral adipose tissue, improvements in insulin sensitivity and other risk factors."

• Exercise and a balanced diet can effectively reduce body and abdominal fat and improve health markers even without weight loss.

"The problem is not achieving weight loss. I would say most Canadians who have tried to lose weight have been successful in doing so. The problem is sustaining that weight loss."

• The primary issue is maintaining weight loss due to environmental and biological factors.

• Studies show benefits of exercise without weight loss, such as reduced cardiometabolic risk factors.
• The societal perception equates exercise success with weight loss, which is not always necessary for health benefits.
• Clinical guidelines are evolving to emphasize healthy behaviors over weight loss.

"While weight loss is certainly associated with benefit, it's not required for benefit."

• Health benefits can be achieved through exercise and diet without necessarily losing weight.

"The canadian obesity guidelines... there's far greater emphasis now than previous guidelines on the importance of adopting the healthy behaviors."

• Guidelines are shifting focus from weight loss to the adoption of healthy behaviors for long-term health benefits.

• Quick measurement of progress, like weighing oneself, is common but doesn't reflect all health benefits.
• Waist circumference and cardiorespiratory fitness are valuable measures of health progress.
• Long-term engagement in healthy behaviors is essential for sustained benefits.

"One is, of course, waist circumference... The other measure that people can do online... is to estimate your cardiorespiratory fitness."

• Waist circumference and fitness levels are practical tools for assessing health improvements beyond weight loss.

"If you engage the behaviors with long term goals... slowly but surely, that waist circumference will come down."

• Long-term commitment to healthy behaviors leads to gradual but meaningful health improvements.

• Discussion on the importance of exercise parameters: frequency, intensity, and duration.
• Evidence from randomized controlled trials is needed to understand the impact of these parameters on health outcomes.
• The focus is on how these parameters affect visceral fat, adipose tissue, and body weight.

"Our knowledge is increasing, but we need more evidence."

• More research is needed to determine the most effective exercise parameters for health improvements.

"If I fix, if I hold constant the amount of exercise..."

• Understanding the specific impacts of exercise frequency, intensity, and duration requires controlled studies.

• The discussion centers around whether exercise intensity influences the outcomes of exercise when the total caloric expenditure is fixed.
• The hypothesis is that with fixed caloric expenditure, the intensity may not significantly alter lipid mobilization.
• Studies indicate that fixed caloric expenditure, regardless of intensity, does not lead to different fat loss outcomes.

"If you fix the amount, alter the intensity, the mobilization of lipid fuel for your exercise, well, probably will not be materially different."

• The quote suggests that altering exercise intensity without changing the caloric expenditure does not significantly affect lipid mobilization.

"We don't see it. Maybe we're underpowered. Maybe the people in the lower amount group are naively or otherwise reducing caloric intake."

• This highlights the unexpected lack of difference in fat loss when exercise intensity is varied, suggesting other factors might be influencing the results.

• HIIT is discussed as a method that emphasizes high intensity in short bursts, which may improve cardiometabolic risk factors.
• There is evidence that HIIT can improve insulin sensitivity more effectively than lower-intensity exercise.
• The effectiveness of HIIT in improving fitness and glucose management is noted, but its impact on adiposity is less clear.

"In short term studies, I think there's no question that for improving fitness and for improving insulin sensitivity, intensity matters."

• The quote confirms that high-intensity exercise is beneficial for fitness and insulin sensitivity, highlighting the importance of intensity for these outcomes.

"We don't have any hit studies that go for 12-24 months... So the translation of hit as a viable strategy to manage health risk in adults has yet to be shown."

• This emphasizes the current lack of long-term studies on HIIT, raising questions about its sustainability and long-term effectiveness.

• The discussion includes a study comparing resistance, aerobic, and combined exercises in older adults, focusing on insulin resistance and functional mobility.
• Each exercise modality has distinct benefits: aerobic exercise is linked to caloric expenditure, while resistance exercise is associated with muscle mass and function.
• The combination of both modalities was tested to assess their collective impact.

"In older adults... we have an expanded waistline, but we have muscle mass loss and muscle function loss. So sarcopenia and what we now call dynapenia."

• This quote highlights the dual challenges of obesity and muscle decline in older adults, which the study aimed to address through different exercise modalities.

"In the combination, we reduced the number of aerobic sessions to three and three, because we just wanted something feasible."

• This explains the practical approach in designing the combination exercise regimen, aiming for feasibility and balanced caloric expenditure.

• Resistance exercise significantly improves functional fitness in older adults, aiding activities like getting out of a chair and walking.
• Aerobic exercise is more effective than resistance exercise in managing blood sugar and reducing adiposity.
• Combining aerobic and resistance exercises is the ideal prescription for improving both functional fitness and blood sugar management.
• Adherence to exercise guidelines is essential for older adults, despite challenges like accessibility and weather conditions.

"Resistance exercise improved functional fitness in all of those in the group, and that was tremendous, but it did little to improve your ability to manage blood sugar."

• Resistance exercise is vital for functional fitness but not effective for blood sugar management.

"Aerobic exercise, right, did not improve functional fitness as much as resistance, but it improved your ability to manage blood sugar."

• Aerobic exercise is crucial for blood sugar management, though less effective for functional fitness.

"The combination of the two turned out to be the ideal prescription, that if you want to improve both of those risk factors, you do the combination."

• A combination of aerobic and resistance exercises is recommended for comprehensive health benefits.

• Aerobic activity, even three times a week, is beneficial for older adults, supporting insulin sensitivity improvements.
• Resistance exercise alone does not significantly differ from control groups concerning insulin sensitivity.
• The importance of aerobic activity is emphasized, especially when combined with resistance training.

"Some might make a slightly different observation, Mark. They may say what that shows is the importance of aerobic activity."

• The significance of aerobic activity is highlighted, especially in improving insulin sensitivity.

"The resistance alone was not different from control."

• Resistance training alone has limited impact on insulin sensitivity compared to control groups.

• The guidelines emphasize a holistic approach, integrating physical activity, reduced sedentary behavior, and good sleep quality.
• The initiative involved an international panel and was launched during the COVID pandemic.
• The guidelines encourage reallocating time from sedentary activities to light or moderate physical activities.
• Emphasize that changes in activity should not compromise sleep quality.

"The principal assertion is that your whole day matters. That's what the 24 hours movement guidelines means."

• The guidelines focus on the importance of daily activity integration for overall health.

"Sit less, move more, is the simple public health message."

• A straightforward message encouraging less sedentary behavior and more movement.

"Never ever do that at the expense of sleep."

• Emphasizes the importance of maintaining good sleep quality alongside physical activity.

• The guidelines offer flexibility, allowing individuals to choose activities that suit their lifestyle and preferences.
• Encourages breaking up sedentary time with light physical activities like walking.
• Highlights that even small amounts of physical activity can provide significant health benefits.
• Promotes a personalized approach to physical activity, empowering individuals to make choices that fit their unique circumstances.

"You can make your day matter in a way that's right for you."

• Encourages personalization in physical activity routines.

"There's benefit all along. As a matter of fact, you get far more benefit going from a sedentary to even 75 minutes in the whole week than you do from 75 to 150."

• Highlights the benefits of even small increases in physical activity.

"It's a dose response association. It's not a threshold."

• Emphasizes that benefits are gained progressively, not just upon reaching a specific target.

• The guidelines aim to provide a flexible framework for physical activity that accommodates individual differences.
• Public health messaging should focus on the cumulative benefits of physical activity rather than strict adherence to specific targets.
• Encourages ongoing research and dialogue to further refine and promote effective health guidelines.

"Almost no matter what you do when you're moving, you're going to gain benefit."

• Reinforces that any increase in physical activity is beneficial.

"We have these targets that if you can achieve, that's fine, but if not, still you can benefit from exercising."

• Acknowledges that while targets are helpful, benefits can still be gained without meeting them fully.