Past, Present, and Future of “Biological Aging” with Dr. Fitzgerald
Interview with David Ludwig, M.D. PhD, Harvard endocrinologist and author of Always Hungry?
After podcasting with Dr. David Ludwig, author of NYT best seller Always Hungry?, I had a few more questions and shot him a couple of emails. I appreciate his thoughtful responses. Here’s what he had to say about calorie counting, ketosis, ideal insulin levels and weight loss resistance. — Kara Fitzgerald.
KF: Do you think there is any utility in monitoring caloric intake? Or are we moving past the era of “counting calories”?
David Ludwig: I suggest completely abandoning calorie counting as a way to control calorie balance. First off, no one, not even professionals, can do it accurately without elaborate technology. An error of +350 kcal per day (within typical error range) would produce massive obesity in a few years. For that matter, if calorie counting were critical to weight management, how did humans manage to avoid massive swings in body weight, before the very concept of the calorie was invented a century ago? Instead, we put the entire focus on creating the right internal conditions for weight loss (right diet and related supports), and let the process happen naturally — with the body’s active cooperation, not with the body kicking a screaming.
KF: Weight loss resistance. A subset of my patient population (generally, peri- and postmenopausal women) has significant difficulty losing weight, or moving into any degree of ketosis. Any thoughts on what’s occurring here?
David Ludwig: Hard to generalize. I’ve argued in my book that most people show resistance to weight loss on a typical low fat diet, because the resulting high insulin secretion tends to lock calories into fat cells. That said, there is of course much individual variation, based on many factors: genes, early life “programming”, health issues, physical activity and stress levels, etc. As to whether this is more pronounced in perimenopausal women, we don’t have much data.
KF: Is there an optimal fasting insulin number or range that you like to see? I generally look at 5 uU/mL or below as being optimal, based on San Antonio Heart Study data.
David Ludwig: For fasting insulin, generally speaking, the lower the better. Less than 5 uU/mL is not bad, though someone in great metabolic health typically has a fasting insulin of 2 or less. Keep in mind that insulin level in the blood doesn’t tell us anything about tissue insulin sensitivity. Thus, the combination of high sensitivity in the fat and low sensitivity in muscle would be much worse than the opposite, even though serum levels could be similar.
KF: Ketosis. You described challenges transitioning in/out of ketosis. And therefore don’t promote it. Can you expound on that? Are you speaking of very high levels of ketone production consistent with a ketogenic diet? For some (many?) a simple, normal overnight fasting period results in mild ketosis.
David Ludwig: Yes, I’m talking about nutritional ketosis (ketone levels above 0.5 mM), which involves a transition from using carbohydrate to fat as the main fuel for the brain. Depending on metabolic state, some people may feel poorly when making this transition.
Listen to the full podcast here.
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