XY Files

Evidence-based articles on testosterone, men's health, fitness, longevity, and sexual health.

Editors' picks

Can you chew gum while fasting? What it means for ketosis and autophagy

Dr. Susan Carter, MD: Endocrinologist & Longevity Expert

Jan 08, 2026 · 9 min read

Sugar-free gum is usually compatible with a ketosis-focused fast because one piece is typically a negligible caloric input (often kept under ~30 calories total during the fasting window), but any calorie- or sugar-containing gum can blunt a stricter fast aimed at autophagy, where the safest approach is staying truly calorie-free. The key is how many ...

Joe rogan supplements: Which pills actually boost performance and which are just hype?

Dr. Bruno Rodriguez, DPT, CSCS: Strength, Recovery, and Physical Therapy Expert

Dec 30, 2025 · 10 min read

Creatine monohydrate is the most consistently performance-boosting supplement in Rogan’s stack because it raises muscle phosphocreatine to regenerate ATP during high-intensity training, while most OTC “testosterone boosters” and trendy biohacks are largely hype without a true deficiency or prescription therapy. Here’s an evidence-based breakdown of what actually moves the needle for male physiology—and what just ...

How do you measure your penis correctly, according to a urologist

Dr. Alexander Grant, MD, PhD: Urologist & Men's Health Advocate

Dec 09, 2025 · 13 min read

Urologists measure penis length as “bone‑pressed” length—press a rigid ruler into the pubic bone on the top side and measure straight to the tip (glans)—and measure girth by wrapping a tape measure around the mid‑shaft; with this standardized method, the average erect length is about 5.1–5.5 inches and the average erect girth is about 4.8 ...

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Latest medical insights

Do weight loss supplements work for men? separating the science from the scam

The best weight loss supplements for men are the ones with human evidence, modest expectations, and a clear mechanism — and green tea extract is one of the few that consistently shows a signal in research. This guide breaks down what “works” really means, how to use supplements safely, and what numbers to track so ...

Got “Normal” testosterone on Function Health but still feel off? How to interpret results and plan next steps.

A testosterone result can be “normal” and still feel off because testosterone deficiency is diagnosed by symptoms plus consistently low morning total testosterone on repeat testing (often around ~300 ng/dL), and total testosterone can look adequate while free testosterone is low when SHBG is elevated. Here’s how to decide when a repeat draw matters, which ...

Keto diet and CGM: what your glucose level can look like and how to avoid reverse metabolic inflexibility

On a ketogenic diet, CGM traces usually show a lower, flatter 24‑hour glucose curve, while a rare high‑carb meal can cause a higher peak and slower return to baseline because fat adaptation temporarily downshifts rapid glucose disposal (“reverse metabolic inflexibility”) rather than proving true insulin resistance. Learn how to interpret trends despite interstitial‑fluid lag and ...

Blueprint stack review: what Bryan Johnson’s simplified longevity stack can and can’t do for men

Bryan Johnson’s commercial “Blueprint Stack” promises a simplified route into a longevity-focused routine. This blueprint stack review breaks down what’s actually in the stack as described, what the research says about the major components for men, and how to use a “stack” approach without drifting into expensive guesswork. “If a ‘stack’ helps you consistently hit ...

The hidden link between inflammation and heart disease: Why cholesterol is only half the story

Chronic arterial inflammation can turn LDL-based plaque dangerous by driving cytokine signaling (IL‑1β, IL‑6) that recruits macrophages and releases metalloproteinases to thin the fibrous cap until it ruptures, which helps explain why nearly 50% of heart attacks occur in men with “normal” cholesterol. A standard lipid panel won’t capture that risk, so this article breaks ...

Building muscle after 40: The science of getting stronger when recovery slows down

Men over 40 can still build muscle and strength, but anabolic resistance and slower tissue repair often extend recovery from heavy sessions to roughly 48–72 hours, meaning the hypertrophy stimulus has to be higher to meaningfully trigger muscle protein synthesis. Here’s how to adjust training volume and target 30–40 g of high‑quality protein (~3–4 g ...

Bulking vs cutting: The science of body recomposition for men

Bulking and cutting work by deliberately shifting energy balance: a 250–500 calorie daily surplus supports muscle protein synthesis and hypertrophy, while a sustained calorie deficit drives fat oxidation but can increase muscle protein breakdown. The key to body recomposition is committing to one clear signal for 12–16 weeks—rather than chasing muscle gain and leanness at ...

Best supplements for inflammation in men: what works, what’s safe, and how to choose

For most men, the best-supported supplement for reducing chronic, systemic inflammation is omega‑3 fish oil (EPA+DHA), which can shift eicosanoid signaling toward fewer pro‑inflammatory mediators and is typically studied at about 1–4 g/day taken with food. Here’s how to choose an evidence-based option (and dose) based on your main risk drivers and inflammation markers like ...

Testosterone and the Dietary Guidelines for Americans: what men should actually do

The phrase “testosterone dietary guidelines americans” sounds like a niche search query. But it reflects a real shift: more men are looking to federal nutrition guidance for answers about hormone health. The Dietary Guidelines for Americans (DGA) doesn’t set testosterone targets, but its focus on weight and cardiometabolic health overlaps with factors associated with testosterone ...

Brain fog in men: the best vitamins for brain fog and memory and the supplements that actually make sense

The most evidence-based vitamins for brain fog and memory in men are B12 (often alongside folate and B6) to correct deficiency and reduce homocysteine, plus vitamin D when status is low, because these pathways support brain energy metabolism, neurotransmitter function, and immune-driven inflammation control. Here’s how to tell when “brain fog” is a fixable signal ...

At what age does a man stop ejaculating? understanding the changes in your body

There is no specific age when a man stops ejaculating, and many men can ejaculate throughout life, though semen volume and the “force” of ejaculation often decline with age.,[1] If ejaculation changes suddenly or stops completely, it is worth getting checked because the cause is often identifiable and treatable. “Most men don’t hit a birthday ...

Athlete biomarker testing for longevity: the lab numbers that keep men performing longer

For longevity-focused men who train, repeating key labs—especially HbA1c (a ~3‑month average of blood sugar) and ApoB (the number of atherogenic particles that can enter artery walls)—can reveal early metabolic drift and cardiovascular risk before performance drops or disease shows up. Pair those with iron, inflammation, and hormone/recovery markers to build a “healthspan dashboard” that ...

What muscles does cycling work? A physiologist’s guide to building power

Cycling primarily works the quadriceps, gluteus maximus, and hamstrings, while the core and hip–lower back stabilizers brace the pelvis to transfer force through a closed-kinetic-chain pedal stroke. If you only push down on the pedals you can leave “half your potential power” unused and increase knee load—here’s how biomechanics and bike fit help you recruit ...

Weights or cardio first? The evidence-based order that gets men results faster

For most men trying to build strength and muscle, do weights first and finish with cardio, because cardio-first increases fatigue and AMPK signaling (and can drain glycogen), which can reduce lifting volume and potentially blunt mTOR-driven hypertrophy. If endurance is your main goal or you’re splitting sessions across the week, the “best” order changes—here’s how ...

How long does it take to lose muscle? The science of detraining

Measurable muscle atrophy typically doesn’t begin until about 2–3 weeks of complete inactivity, with the first 5–7 days off usually reflecting depleted glycogen and water rather than lost contractile tissue. The real risk window—and why immobilization (bed rest or a cast) changes the timeline—comes down to how quickly protein synthesis drops when mechanical tension disappears. ...

Best push pull legs routine for muscle gain: how to run a push pull legs split without wrecking your joints

For most healthy men, a push pull legs split is one of the best push pull legs routines because it organizes training around movement patterns, distributes weekly volume efficiently, and builds in recovery so you can progress without living sore. The key is matching the split to your schedule, then using evidence-based volume, intensity, and ...

Worst foods for erectile dysfunction: how your diet affects your erection quality

Diets high in processed sugars, trans fats, and excessive sodium (a typical “Western diet”) can worsen erectile dysfunction by damaging the endothelium and reducing nitric oxide–driven vasodilation needed to fill and trap blood in the penis. Because penile arteries are smaller and show vascular injury earlier than the heart, your grocery list can affect erection ...

Is BRI better than BMI? The new longevity metric men need to know

The Body Roundness Index (BRI)—a 1–16 score calculated from height and waist circumference—has outperformed BMI in large studies at predicting all-cause mortality because it captures abdominal “roundness” tied to visceral fat. If BMI has mislabeled your physique or missed hidden belly-fat risk, BRI shows what your shape says about your metabolic health and longevity. “We ...

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Medical podcast

Listen to the latest episodes on men's health, hormones, performance, and longevity.

Episode 6: Honey packs for men: what they are, how long they last, and the hidden risks

February 10, 2026 · 10:01

Many honey-pack male enhancement sachets contain undeclared PDE5 inhibitors and can dangerously lower blood pressure.

Episode 5: The best multivitamin for men over 50: how to choose between popular brands like nature made and centrum

February 03, 2026 · 10:25

How to choose a multivitamin for men over 50 by matching formulas to diet, meds, and biology; Nature Made vs Centrum.

Episode 4: Are peptides legal? What the new FDA regulations mean for you

January 27, 2026 · 9:41

FDA restricted compounding of many peptides, placing 17 off-limits for human use and prioritizing evidence-based care.

Episode 3: Is Dave’s Killer Bread healthy or just hype?

January 23, 2026 · 10:39

An endocrinologist assesses whether Dave's Killer Bread's fiber and protein benefits outweigh added calories and sugars.

Episode 2: Your guide to effective testosterone replacement therapy near me

January 20, 2026 · 10:49

This episode guides diagnosing low testosterone, realistic TRT benefits, and finding safe, evidence-based local care.

Episode 1: Facing the truth: My experience with testosterone replacement therapy side effects

January 19, 2026 · 10:42

Evidence-based look at TRT side effects and the monitoring steps needed to manage them safely.

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Medical knowledge hub

Fertility & reproductive health

Navigate conception with clarity and science. Explore semen analysis, male infertility evaluations, and preparation for assisted reproduction like IVF and IUI. Learn how hCG, enclomiphene, and targeted supplements can improve sperm count, motility, and semen quality. Clear, evidence-based guidance to improve fertility and reproductive outcomes.

Fitness & physical performance

Train with your hormones, not against them. We cover strength, hypertrophy, VO2 max, recovery, and injury prevention through an endocrine lens. Discover how training, nutrition, and daily activity can impact testosterone levels and support natural balance. Use estradiol balance for joint health, plan sleep taper cycles before competitions, and turn smart physiology into new PRs.

Lifestyle & longevity

Design daily habits that support hormonal balance and long-term vitality. Master sleep and circadian timing, eat for metabolic stability, and use micronutrients with purpose. Make informed choices about alcohol, nicotine, sauna, and cold exposure. We translate longevity research into clear, practical playbooks you can apply today.

Mental health

Everything you need to know about how hormones shape mood, focus, and emotional balance. We explore anxiety, depression, ADHD, stress response, and cognitive performance through the lens of neuroscience and endocrinology. Learn how to stabilize cortisol, support healthy testosterone levels, and rebuild mental clarity.

Sexual health

Start with what matters: desire, function, and comfort. We explain libido, arousal, erectile function, orgasm, and sexual pain, and how medicines and hormones influence them. Clear language, evidence-based guidance, and practical steps to understand your body and improve sexual well-being.

Testosterone 101

Everything you need to know about testosterone, backed by the latest research. We turn complex topics like diagnosis, dosing, delivery methods, and lab results into simple, practical insights. Understand TRT benefits and risks, maintain estradiol balance, and spot drug interactions - all grounded in evidence, not hype.

Authors and medical reviewers

Dr. Alexander Grant, MD, PhD: Urologist & Men's Health Advocate

Dr. Alexander Grant is a urologist and researcher specializing in men's reproductive health and hormone balance. He helps men with testosterone optimization, prostate care, fertility, and sexual health through clear, judgment-free guidance. His approach is practical and evidence-based, built for conversations that many men find difficult to start.

Dr. Bruno Rodriguez, DPT, CSCS: Strength, Recovery, and Physical Therapy Expert

Dr. Bruno Rodriguez designs strength and recovery programs for professional athletes and patients recovering from surgery. He focuses on building strength, mobility, and effective recovery while lowering injury risk. His goal is for men to achieve the best performance in the gym and in daily life.

Dr. Jonathan Pierce, PhD: Clinical Psychologist & Neuroscience Specialist

Dr. Jonathan Pierce integrates clinical psychology with neuroscience to connect mood, motivation, and hormones. He helps men manage stress, low drive, and anxiety, then builds durable habits for focus, resilience, and performance at work and at home.

Dr. Susan Carter, MD: Endocrinologist & Longevity Expert

Dr. Susan Carter is an endocrinologist and longevity expert specializing in hormone balance, metabolism, and the aging process. She links low testosterone with thyroid and cortisol patterns and turns lab data into clear next steps. Patients appreciate her straightforward approach, preventive mindset, and calm, data-driven care.