Optimal Protein Podcast with Vanessa Spina

Does burning more fat for fuel mean you're actually losing more body fat? And if you're in ketosis, does that mean the fat you're burning is coming from your body—or from the food you just ate?
Today on the Optimal Protein Podcast, I'm joined by Dr. Mike T. Nelson to unpack this important distinction and explore what metabolic flexibility really means for fat loss, muscle preservation, and performance.
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Mike holds a PhD in exercise physiology and a master's degree in mechanical engineering with a focus on biomechanics. In this fascinating conversation, we explore your body's ability to use both carbohydrates and fat, switch between them, and adapt to different demands.
We discuss why burning more fat during a workout doesn't necessarily translate into greater body-fat loss, why calorie balance still matters, and how your nutrition and training can work together to support body recomposition. I also share my own experience gaining weight on keto despite high ketone readings—and what that taught me about dietary fat versus stored body fat.
In this episode, we discuss:
• The three components of metabolic flexibility—and why using carbohydrates effectively matters, too
• Burning fat versus losing fat: the distinction that can change how you approach your goals
• How insulin and fuel availability influence what your body burns
• Why higher ketone readings don't necessarily mean greater body-fat loss
• Fasted cardio: what the research suggests and where questions remain
• Long-term keto and the potential tradeoffs for high-intensity exercise
• Adjusting carbohydrates to support your training performance
• Protein-sparing modified fasting and the considerations around more aggressive calorie deficits
• Why stubborn lower-body fat can be especially frustrating for women
• Protein and resistance training: their roles in preserving lean mass while dieting
• Building aerobic fitness to support metabolic flexibility over time
• Heat, cold exposure, and Mike's broader framework of physiologic flexibility
• Lactate as a valuable fuel and the emerging interest in lactate supplements
• Tracking performance alongside the scale—and keeping maintenance in mind from the beginning
I loved Mike's emphasis on building a body that can perform well while you work toward your body-composition goals. This episode is full of thoughtful distinctions to help you better understand the science behind fat loss!
Connect with Dr. Mike T. Nelson:
Instagram: @drmiketnelson
Explore his newsletter for more on body composition, performance, and metabolic flexibility.
Special offers mentioned in this episode:
Save 40% sitewide at ⁠KetogenicGirl.com with code BACKTOSCHOOL40, including the Protein-Sparing Modified Fasting Library and Tone Device.
Australia and New Zealand listeners: save 75% during the warehouse moving sale with code WAREHOUSE75.
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The content provided in this podcast is for informational purposes only and should not be construed as medical advice. Consult with a healthcare professional before making significant changes to your diet, supplements, or exercise regimen.

Can you gain lean tissue while losing body fat? And if two people eat the same number of protein grams, will they necessarily get the same body composition results?
In this episode, Vanessa shares six takeaways from her conversation with Dr. Drew Gonzalez on the science of fat loss, muscle retention, protein quality, creatine, and sustainable nutrition.
BACK-TO-SCHOOL SALE! For a limited time, save 40% sitewide at ketogenicgirl.com⁠ with code BACKTOSCHOOL40, including the Protein-Sparing Modified Fasting Library, ToneLUX Red Light Therapy Collection, and Tone Breath Ketone Analyzer.
A 12-week study discussed in the interview found that adults combining an exercise and weight-loss program with creatine gained lean tissue while reducing body fat. Vanessa unpacks why that result is exciting, what "lean tissue" actually measures, and why the change in body fat percentage needs careful interpretation.
In this episode:
Why the quality of weight loss matters more than the number on the scale alone
What the creatine study found about lean tissue and body fat during a weight-loss program
Whether protein quality may matter more when calories are limited
What a study comparing pork- and soy-based meals in military cadets found about recovery
How much protein Dr. Gonzalez suggests as a practical starting goal for people who resistance train
Why you don't need perfectly timed or evenly divided protein meals
What firefighter research can—and cannot—tell us about time-restricted eating
Where the evidence stands on creatine and cognition, probiotics, and other emerging supplements
The central question: How can you lose body fat while giving yourself the best chance of maintaining—or even gaining—lean tissue?
Listen to Vanessa's full interview with Dr. Drew Gonzalez for the complete conversation.
Follow @ketogenicgirl and @optimalproteinpodcast on Instagram, and join the Optimal Protein Podcast Facebook group to continue the discussion.
BACK-TO-SCHOOL SALE! For a limited time, save 40% sitewide at ketogenicgirl.com⁠ with code BACKTOSCHOOL40, including the Protein-Sparing Modified Fasting Library, ToneLUX Red Light Therapy Collection, and Tone Breath Ketone Analyzer.
The content provided in this podcast is for informational purposes only and should not be construed as medical advice. Consult with a healthcare professional before making significant changes to your diet, supplements, or exercise regimen.

Can you lose body fat while gaining lean tissue—even during a calorie deficit? And could the quality of your protein change how well you recover and protect muscle?
Vanessa is joined by exercise and nutrition researcher Dr. Drew Gonzalez to explore new research on creatine, body recomposition, protein quality, and what it takes to make weight loss more than a lower number on the scale.
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They begin with a 12-week study in middle-aged and older adults that tested creatine alongside exercise and a weight-loss diet. Vanessa and Dr. Gonzalez discuss the promising body-composition findings, why gaining lean tissue is not necessarily the same as gaining that amount of muscle, and what the study can—and cannot—tell us about fat loss and cognitive health.
They also explore research comparing pork- and soy-based meals during intense training, the role of essential amino acids and leucine when calories are limited, and practical protein targets for people who want to lose fat without unnecessarily losing muscle.
In this episode:
What a new creatine study found about lean tissue and body fat during weight loss
Whether someone eating plenty of meat still stands to benefit from creatine supplementation
What we know—and don't yet know—about higher creatine doses and brain health
Why two diets with the same protein grams may differ in essential amino acid content
What Dr. Gonzalez's military cadet study found about protein sources and recovery
How much protein to aim for while resistance training and losing body fat
Whether protein needs to be evenly distributed across meals
What firefighter research reveals about time-restricted eating in demanding real-world conditions
Whether probiotics and synbiotics meaningfully add to a structured fat-loss program
The goal isn't simply to lose weight. It's to improve what you lose—and what you keep.
BACK-TO-SCHOOL SALE! For a limited time, save 40% sitewide at ketogenicgirl.com with code BACKTOSCHOOL40, including the Protein-Sparing Modified Fasting Library, ToneLUX Red Light Therapy Collection, and Tone Breath Ketone Analyzer.
Follow @ketogenicgirl and @optimalproteinpodcast on Instagram, and join the Optimal Protein Podcast Facebook group for more discussion.
The content provided in this podcast is for informational purposes only and should not be construed as medical advice. Consult with a healthcare professional before making significant changes to your diet, supplements, or exercise regimen.

Vanessa breaks down the biggest scientific takeaways and most actionable gems from her recent conversation with body-composition expert and author Lyle McDonald.
Why does fat come off easily from some areas while other areas seem determined to hold on? And can we influence stubborn fat loss without simply getting leaner everywhere else?
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Vanessa explores the physiology of stubborn body fat, including fat mobilization, blood flow, oxidation and alpha-2 receptors, and why women in particular may notice their upper body becoming lean long before their hips and thighs.
She also breaks down Lyle's newest approach, Intermittent Modified Fasting, and how alternating protein-focused, low-calorie days with maintenance days may offer a more flexible way to create a calorie deficit while prioritizing muscle retention.
Vanessa explains why protein becomes especially important during aggressive calorie restriction, why a maintenance day is different from a "cheat" or "feast" day, and how meal timing, appetite and ketosis can influence how sustainable a fat-loss phase feels.
She also examines Lyle's proposed strategies for addressing stubborn fat—including lower-carbohydrate eating and combining higher-intensity intervals with lower-intensity activity—while separating established physiology from strategies that still require more research.
YOHIMBINE SAFETY NOTE: Yohimbine is discussed in this episode for educational purposes only and is not being recommended for use. Yohimbine can cause significant side effects, including anxiety, increased heart rate and blood pressure, and may interact with medications. It should not be used during pregnancy or breastfeeding. Anyone considering yohimbine should first consult with a qualified healthcare professional.
Finally, Vanessa explores the scientific mechanisms behind yohimbine and alpha-2 receptors for educational purposes, red-light therapy and blood flow, whether slower weight loss could help preserve facial fullness, and why having a maintenance strategy may be just as important as having a fat-loss strategy.
In this episode:
Why some areas of body fat are more resistant to fat loss
Why women may lose upper-body fat before hip and thigh fat
Alpha-2 vs. beta receptors and stubborn-fat physiology
Fat mobilization vs. fat oxidation vs. actual body-fat loss
Why blood flow matters in stubborn fat stores
Protein-Sparing Modified Fasting (PSMF) explained
Lyle's Intermittent Modified Fasting approach
Why protein matters on very-low-calorie days
Maintenance days vs. cheat or feast days
How to structure lower-calorie and maintenance days around training and life
Why meal timing should help manage your appetite
Time-restricted eating vs. intermittent modified fasting
Protein, ketosis, satiety and food preoccupation
Lower-carbohydrate eating and stubborn-fat mobilization
Higher-intensity intervals followed by lower-intensity activity
Why walking may fit into Lyle's stubborn-fat protocol
Why more cardio is not necessarily better during aggressive dieting
Red-light therapy, blood flow and what the evidence does—and does not—show
Yohimbine, alpha-2 receptors and important safety considerations
Why mobilizing more fat does not guarantee greater fat loss
Resistance training and preserving lean mass during fat loss
How to create a long-term weight-maintenance range
Why small course corrections may help prevent larger weight regain
Can slower weight loss help preserve facial fullness?
Genetics, aging and individual patterns of fat loss
Why your leanest possible weight may not be where you look or feel your best
Vanessa's practical takeaways for sustainable fat loss and body recomposition
BACK TO SCHOOL SALE! For a limited time, save 40% sitewide at ketogenicgirl.com with code BACKTOSCHOOL40, including the Protein-Sparing Modified Fasting Library, ToneLUX Red Light Therapy Collection, and Tone Breath Ketone Analyzer.
Australia, New Zealand & Southeast Asia: Save 75% on available ToneLUX and Tone products during the warehouse moving sale with code WAREHOUSE75, while supplies last.
Follow @ketogenicgirl and @optimalproteinpodcast on Instagram to see visuals and posts mentioned on the podcast.
Link to join the Facebook group for the podcast.
The content provided in this podcast is for informational purposes only and should not be construed as medical advice. Consult with a healthcare professional before making significant changes to your diet, supplements or exercise regimen.

Why does body fat disappear quickly from certain areas while seeming almost impossible to lose from others?
BACK TO SCHOOL SALE! For a limited time, save 40% sitewide at ketogenicgirl.com with code BACKTOSCHOOL40, including the Protein-Sparing Modified Fasting Library™, ToneLUX Red Light Therapy Collection and Tone Breath Ketone Analyzer.
Australia, New Zealand & Southeast Asia: Save 75% on available ToneLUX and Tone products during the warehouse moving sale with code WAREHOUSE75, while supplies last.
In today's episode of the Optimal Protein Podcast, Vanessa welcomes renowned author and body-composition expert Lyle McDonald to explore the fascinating physiology of stubborn body fat.
Where we store our most resistant fat varies from person to person. For some women, it may be concentrated around the hips and thighs; for others, it may be the abdomen, arms or another area. Men may also struggle with stubborn fat, commonly around the abdomen and lower back.
Lyle explains how differences in alpha-2 and beta receptors, blood flow, insulin sensitivity and catecholamine activity can make certain fat stores more difficult to access than others. They break down the three essential steps required to lose stored body fat: mobilizing fatty acids from the fat cell, transporting them away and ultimately oxidizing them for energy.
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Vanessa and Lyle also discuss whether low-carbohydrate eating, ketosis, high-intensity intervals and strategically timed low-intensity activity may help improve stubborn-fat mobilization.
Lyle introduces his new book, Intermittent Modified Fasting, and explains how alternating protein-sparing modified fasting days with maintenance days may support fat loss, muscle retention, training performance and long-term adherence—without dieting continuously.
Yohimbine can cause anxiety, increased heart rate, blood-pressure changes and other adverse effects, and may interact with medications. This podcast discusses the scientific rationale behind alpha-2 receptor antagonists, including yohimbine, for educational purposes only—not as a recommendation for use. Yohimbine is not appropriate for everyone, particularly people with certain medical conditions, and should not be used during pregnancy or breastfeeding. Consult a qualified healthcare professional before considering its use.
In this episode, they discuss:
• Why certain areas of body fat are more resistant than others
• How stubborn-fat patterns differ between individuals
• Why some women struggle most with hip and thigh fat
• Why the abdomen and lower back are common stubborn areas in men
• Alpha-2 versus beta receptors and how they affect fat mobilization
• Why blood flow matters when attempting to access stubborn fat
• The three steps required to mobilize and burn stored body fat
• Why the face and upper body may become lean before stubborn areas
• Whether slower weight loss may help preserve facial fullness
• How low-carbohydrate eating may influence alpha-2 receptors
• Why high-intensity intervals may improve stubborn-fat mobilization
• Pairing short intervals with low-intensity cardio or walking
• Why a calorie deficit is still required for net fat loss
• Protein-sparing modified fasting versus conventional fasting
• Why many alternate-day fasting plans provide too little protein
• How to alternate modified fasting days with maintenance days
• Why "maintenance day" may be more helpful than "feast" or "cheat day"
• Using PSMF days to support long-term weight maintenance
• Ketosis, appetite suppression and the metabolic fasting response
• Yohimbine HCl, alpha-2 receptors and important safety concerns
• Pregnancy, breastfeeding and changes in female fat distribution
If you have ever wondered why one part of your body becomes lean while another area remains frustratingly resistant, this episode explains the biology of stubborn fat—and the strategies that may help create a more balanced pattern of fat loss.
Today's episode is brought to you by Cure Hydration.
Learn more about Lyle and his books at bodyrecomposition.com and store.bodyrecomposition.com.
Follow @ketogenicgirl and @optimalproteinpodcast on Instagram to see visuals and posts mentioned on the podcast.
Join the Facebook group for the podcast.
The content provided in this podcast is for informational purposes only and should not be construed as medical advice. Consult a healthcare professional before making significant changes to your diet, supplements or exercise regimen.