In this episode of Longevity By Design, Dr. Blander sits down with Dr. Mitch Roslin to discuss insulin resistance. Insulin resistance has been top of mind for Dr. Blander recently, and this conversation offers new insights into how we can prevent insulin resistance through diet and lifestyle. Dr. Roslin parses out the different factors that cause insulin resistance, explaining that some are within our control (diet and lifestyle) while others are not (age and genetics). Dr. Roslin also talks about his clinical experience as a bariatric surgeon, sharing insights on how to manage weight and prevent obesity. He gives his expertise on how to eat optimally for metabolic health and answers questions about the ketogenic diet and intermittent fasting.
- Introduction: (0:00–2:45)
- Insulin’s most important role in the body: (2:46–5:35)
- What does it mean to be insulin resistant?: (5:35–7:15)
- What causes insulin resistance?: (7:15–9:00)
- Fasting insulin is an early warning sign for disease: (9:00–11:45)
- Dr. Roslin’s clinical experience with obesity: (11:45–14:25)
- Body fat is not a bad thing: (14:25–16:55)
- Insulin levels impact where fat is stored in the body: (16:55–19:35)
- How can we prevent insulin resistance?: (19:35–21:35)
- Dr. Roslin’s thoughts on the ideal diet: (21:35–22:35)
- Benefits of going for a walk after you eat: (22:35-23:55)
- Diet vs. exercise for weight loss: (23:55–26:45)
- Does the keto diet prevent insulin resistance? : (26:45–28:45)
- Time-restricted eating for weight management: (28:45–33:15)
- Psychology of obesity: (33:15–39:40)
- Does insulin resistance make it harder to lose weight? (39:40–41:43)
- What form of exercise is best to prevent insulin resistance? (41:43–46:05)
- How do we objectively identify insulin resistance?: (46:05–48:30)
- PCOS: (48:30–50:45)
- Defining “healthy”: (50:45–52:45)
- Wrap-up: (52:45-end)
About Dr. Mitchell Roslin
Mitchell Roslin, MD, FACS, FASMBS, is the Chief of Bariatric Surgery at Lenox Hill hospital in New York City and has dedicated his professional career to the treatment of morbid obesity. Dr. Roslin is the editor of the VideoTextBook of Bariatric Surgery, serves as the major teaching proctor for sleeve gastrectomy and duodenal switch, and is the course director for symposiums on revisional bariatric surgery. Dr. Roslin is an innovator in the search for better treatments and holds several patents in the emerging field of Pacing Technology for the treatment of obesity. Dr. Roslin recently has been selected as one of the best minimally invasive surgeons in New York.
Insulin's function in the body
Often linked to diabetes and glucose control, insulin holds a multifaceted significance within the human body. Dr. Roslin explains insulin as the body's “rapid energy hormone,” pointing out that its ability to regulate fat storage is as sentinel as its ability to control blood glucose levels. Dr. Roslin explains that elevated insulin levels at rest signal fat accumulation within the body.
How does insulin resistance increase fat storage?
To best understand the impact of insulin resistance on body fat, Dr. Roslin compares the response of insulin sensitive and resistant individuals to the same exact meal. When both an insulin resistant and insulin sensitive person consumes an identical meal, their glucose curves appear remarkably similar. This means their blood glucose peaks and then returns to baseline in a similar time frame. However, the individual with insulin resistance requires a greater amount of insulin to manage this blood glucose spike. Although glucose regulation has been accomplished in both individuals, the insulin resistant person will experience repercussions due to the increased amount of insulin required to achieve glucose regulation. Insulin resistance’s most profound effect is heightened fat storage, particularly in regions where excess fat poses a health risk, such as the liver, pancreas, and brain.
The importance of testing fasted insulin
Insulin resistance is often a precursor to type 2 diabetes. Insulin resistance is characterized by the body's reduced response to insulin, which leads to higher levels of insulin in the blood. Type 2 diabetes, on the other hand, emerges when blood sugar levels remain consistently high due to the body's inability to properly regulate glucose. If left unaddressed, insulin production is affected. Research suggests insulin resistance precedes type 2 diabetes by 10 to 15 years. 
Throughout the conversation with Dr. Roslin, he discusses the value in testing fasting insulin. He argues that there has been so much emphasis on the consequences of high blood sugar and diabetes that hyperinsulinemia—or insulin resistance—has not received enough attention. “Hyperinsulinemia [itself] has significant consequences for the body too, including poor fertility, fatty liver disease, and possibly dementia,” says Dr. Roslin. He posits hyperinsulinemia may be related to cancer growth because insulin is a growth hormone. “Insulin promotes growth and fat storage, so everything that's related to a high metabolism is probably related to an increase in insulin levels,” Dr. Roslin explains.
What causes insulin resistance?
Dr. Roslin shares that insulin resistance develops over time and there are multiple factors that can impact how sensitive the body is to insulin.
- Age: The body becomes more insulin resistant as you age.
- Genetics: There is a genetic tendency to become insulin resistant, meaning your genetics may put you at a greater risk for developing insulin resistance.
- Diet and lifestyle: Unhealthy eating patterns and a sedentary lifestyle increases the risk for developing insulin resistance.
While there are certain aspects of insulin resistance that individuals can't change (age and genetics), lifestyle modifications can significantly prevent this condition. By understanding how diet and exercise prevent high insulin, people can make more informed decisions about their health.
Health benefits of exercise
Dr. Roslin is a huge proponent of exercise due to its well-known impact on healthspan. He talks about how different forms of exercise can help prevent chronic diseases while also improving the number of healthy, quality years people have. Exercise promotes a healthier longer life in many ways, including:
- Reduced insulin resistance: Dr. Roslin recommends cardiovascular exercise for preventing insulin resistance. More specifically, he says to regularly engage in zone 2 training. Zone 2 exercise involves training at 60-70% of your max heart rate—a pace where you can hold a conversation for 30+ minutes.
- Healthy weight loss: For those who want to lose weight, Dr. Roslin says cardiovascular exercise is critical. This is because aerobic exercise accelerates calorie burn, which is necessary for weight loss.
- Overall healthspan: A mixture of cardiovascular and resistance training is best for healthspan. Maintaining bone health is crucial as we age, and resistance training preserves bone health.
How does exercise prevent insulin resistance?
Dr. Roslin dives deeper into the mechanism by which exercise helps the body manage insulin levels. He explains that glucose can enter cells in two distinct routes: the insulin-dependent pathway and the insulin-independent pathway. The insulin-dependent pathway requires the release of insulin from the pancreas, which then works to push glucose into cells. In contrast, the insulin-independent pathway is promoted by exercise, meaning exercise itself can push glucose into cells. Muscle contractions during exercise enable cells to uptake glucose and use it for energy. Less insulin is required to manage glucose in this pathway, which is why exercise can help prevent insulin resistance.
The optimal diet for metabolic health
In discussing how to eat optimally to promote metabolic health, Dr. Roslin advocates for prioritizing fiber in the diet. He recommends allocating two-thirds of the diet to fiber-rich options, for example, salads, legumes, nuts, and fruit. The other one-third of the diet is protein sources, for example, chicken, turkey, and fish. According to Dr. Roslin, “The more fiber that goes into your food, the healthier you will be.”
Is the ketogenic diet healthy?
Dr. Roslin explains that ketogenic diets can be effective for short-term weight loss. However, a ketogenic diet typically lacks fiber, making it an unhealthy long-term eating pattern. He says that a modified ketogenic diet—one that includes fiber-rich foods but is low in ultra-processed foods and refined grains—can be one way to modify the ketogenic diet to support weight loss without driving insulin resistance.
Is intermittent fasting an effective way to manage weight?
Intermittent fasting is an eating pattern for which an individual will only eat during a short window—for example, 11am to 5pm. Some research suggests intermittent fasting has health benefits independent of caloric restriction . However, Dr. Roslin discusses intermittent fasting as it relates to caloric restriction and weight loss, explaining it as a tool that helps people reduce daily calorie intake. By limiting the eating window to 6-8 hours, calories consumed may be less than what would be consumed in a full day.
Dr. Roslin shares that in his experience, he has seen intermittent fasting to be effective among those with disciplined dietary habits or a genetic predisposition to weight maintenance. For individuals with poor energy regulation—for example, people with severe obesity—intermittent fasting may not be an effective way to manage weight. Dr. Roslin clarifies that these individuals are likely to consume an equivalent, if not greater, quantity of calories during the restricted window than they would during a regular day. He recommends speaking with a doctor or registered dietitian before starting intermittent fasting to see if it's right for you.
- Insulin is an energy-regulating hormone and plays a pivotal role in fat regulation.
- Insulin resistance develops over time. Some risk factors are within our control (diet and exercise), with other risk factors being out of our control (age and genetics).
- Diet and regular exercise is the best way to promote healthspan and prevent insulin resistance.
- For optimal metabolic health, prioritize fiber in your diet.