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Carbohydrate Sensitive Phenotype (CSP): Precursor of the Metabolic Syndrome?

Posted on Tuesday September 23, 2025 in Naked Heart

An article written by Dr Edward Leatham, Consultant Cardiologist

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What is Metabolic Syndrome?

Metabolic syndrome (MetS) is a common and serious health condition that significantly increases the risk of heart disease, stroke, and type 2 diabetes. It refers to a cluster of 3 or more of the following 5 rather general characteristics are present:

Insulin resistance
High blood pressure (hypertension)
Elevated blood glucose
High triglycerides
Low HDL cholesterol (“good” cholesterol)
Abdominal obesity (excess fat around the waist)

Metabolic syndrome is also known as insulin resistance syndrome, reflecting the central role that impaired glucose metabolism plays in its development.

Prevalence in the UK

Metabolic syndrome is increasingly common in the UK:

An estimated 1 in 4 adults is affected, according to the NHS Learning Hub and HEART UK – The Cholesterol Charity¹.
Prevalence rises sharply with age, with 30–40% of adults aged 65 and over meeting diagnostic criteria.
It is strongly linked to overweight, obesity, and especially central (visceral) fat accumulation.

What Drives It?

Lifestyle Factors

Modern sedentary lifestyles and diets high in ultra-processed, high-glycaemic foods are major contributors. These behaviours promote:

Energy imbalance
Insulin resistance
Visceral fat accumulation

Weight Gain

The global obesity epidemic has made metabolic syndrome more prevalent than ever.

Environmental Influences

Emerging evidence suggests that environmental stressors—such as air pollution—may also disrupt metabolic pathways and contribute to risk.

Why It Matters

Metabolic syndrome is not just a collection of risk factors—it’s a powerful predictor of chronic disease. It substantially increases the likelihood of:

Coronary artery disease
Atrial fibrillation
Heart failure
Stroke
Type 2 diabetes

The Case for Early Action

Metabolic syndrome typically develops gradually. That means there’s a window of opportunity for intervention before full syndrome criteria are met. For cardiologists focused on prevention, this has led to a shift: identifying at-risk individuals earlier and intervening proactively.

But what do we call this early stage?

Introducing the Carbohydrate Sensitive Phenotype (CSP)

Carbohydrate Sensitive Phenotype (CSP) is a proposed term to describe a pre-syndromic metabolic pattern commonly seen in patients with:

Waist-to-height ratio (WHtR) > 0.5
Glucose spikes after carbohydrate-rich meals
Normal or borderline weight, blood sugar levels and HbA1c.

CSP is not a diagnosis of diabetes or obesity. Rather, it’s a biologically driven pattern of visceral fat accumulation and carbohydrate intolerance—often triggered by age and Western-style diets.

CSP: A Name That Replaces Shame with Science

For decades, people with central weight gain were labelled as “lazy” or “undisciplined”—judged for their bodies without understanding the biology behind them. CSP reframes that narrative:

It gives people a language to understand what’s happening in their body.
It shifts the focus from blame to biology.
It opens the door to support, not shame—empowering individuals to engage with health and nutrition without guilt.

In summary, early identification of CSP could allow for timely, targeted interventions that delay or even prevent the onset of metabolic syndrome and its complications. Naming the pattern is the first step in changing the story—and improving outcomes.

CSP shifts the narrative. It moves us from moral judgement to metabolic understanding.

It acknowledges that:

Appetite regulation is attenuated in people with CSP
Visceral fat accumulation is hormonally and genetically driven
The modern Western diet overwhelms the carbohydrate tolerance of many people
Even those trying their best may still see glucose spikes and VAT gain

Naming this Carbohydrate Sensitive Phenotype is not only medically useful—it is socially protective.

Just as we accept:

“I’m gluten-free because I have coeliac disease”
“I don’t drink milk because I’m lactose intolerant”

…people should feel equally safe and validated saying:

“I’m avoiding bread—I have CSP.”
“I’m limiting beer— as I have CSP.”
“I’m skipping dessert—I’m managing my CSP.”

These phrases are conversation starters, not excuses. They:

Create space for others to ask questions, not pass judgement
Empower people to make informed, confident food choices
Help break the culture of shame around weight and dietary restraint
Offer medical legitimacy to choices that may otherwise be misunderstood

In this way, CSP becomes not just a clinical term, but a social tool for advocacy, support, and visibility.

Clinical Profile

CSP is a clinically meaningful term for our patients who have:

Raised waist-to-height ratio (>0.5), typically apple-shaped
Post-meal glucose spikes, measurable via CGM
Visceral adipose tissue accumulation
Mild reductions in HDL or mild HbA1c elevations (still in the normal range)
Normal or moderately elevated BMI
Worsening with age, inactivity, stress, or carbohydrate load
Often normal fasting glucose and insulin, despite glucose instability after meals

CSP can be considered to be a precursor to the well described metabolic syndrome.

Recommended Treatments for CSP

Dietary Approach: Modified Harvard Plate

The Harvard Healthy Eating Plate is a sound nutritional foundation, but for CSP patients trying to reduce VAT, it benefits from carbohydrate modification:

CSP-modified Plate:

½ plate non-starchy vegetables
¼ plate lean protein (fish, legumes, poultry, tofu)
¼ plate low-GI carbs (lentils, quinoa, oats) — or none in active fat loss
Eliminate fruit juice, ultra-processed foods, sugary drinks
Use CGM feedback to guide individual tolerance

Exercise Focus: Strength, Core and HIIT

VAT responds best to resistance training, core engagement, and high-intensity intervals:

Strength training: improves glucose disposal via muscle
Core training: enhances trunk control, activation, and function
HIIT: shown to reduce visceral fat faster than steady-state cardio

Pharmacotherapy: Tirzepatide, Semaglutide and GLP-1 RAs

Semaglutide and Tirzepatide (a dual GIP/GLP-1 agonist) are now commonly used in clinical practice in patients with various heart conditions to:

Reduce visceral fat and waist circumference
Suppress appetite and sweet cravings
Improve glycaemic stability and cardiometabolic markers
Preserve lean mass during weight loss
Improve event free survival

This may be appropriate even when labs are “normal”, as many CSP patients have hidden VAT and CGM-confirmed glucose spikes.

Technology Tools for CSP

CGM: visualise individual glucose response to meals
AI food logging apps: real-time nutritional feedback

Waist measurements: better than weight for VAT tracking

Summary

CSP is a highly prevalent, biologically driven phenotype of visceral fat accumulation and post-meal glucose dysregulation.

It does not require low HDL, high fasting glucose, or insulin resistance to diagnose.
What matters is the pattern: central fat gain, food-induced glucose spikes, and modern dietary overload.

Naming the condition helps remove blame and shame, and allows people to communicate dietary needs as confidently as someone with a food allergy or intolerance.

With personalised tools—diet, exercise, GLP-1s, and tech—CSP can be reversed, and lives can be changed.

Optimal Blood Pressure: How Low is Low Enough?

Diastolic heart failure (often referred to as 'Heart failure with preserved Ejection Fraction' or 'HFpEF') arises from ventricular stiffening due to age, hypertension, and various other rarer heart conditions. The aging component of this process is unavoidable, but maintaining optimal blood pressure through midlife is achievable and, if successful, should prevent additional left ventricular stiffening attributed to hypertension. By regularly monitoring blood pressure and using effective medication, we can help patients live longer with healthier hearts.

LDL: the lower the better

Being born with almost no circulating cholesterol (or reduction of LDL to zero by drugs) results in nothing except a zero-lifetime risk of atherosclerosis (or cessation and reduction in atherosclerosis).

Starting betablockers?

For a cardiologist, beta blockers are a commonly used medication, possibly because we live in a high stress world and patients come to us with symptoms that are often improved by moderating the biological effects of our own adrenaline on the systems it was designed to protect.