10 Things GLP-1 Drugs Actually Do to Your Blood Pressure, Glucose, and Body Composition

GLP-1 receptor agonists, including semaglutide (brand names Ozempic and Wegovy) and tirzepatide (Mounjaro and Zepbound), have reshaped the conversation around metabolic health. Originally developed for type 2 diabetes, these medications have shown remarkable effects across multiple metabolic markers. The SELECT trial, published in 2023 in the New England Journal of Medicine, demonstrated that semaglutide reduced major cardiovascular events by 20% in overweight adults. But the full picture of what these drugs do across blood pressure, blood sugar, and body composition is more nuanced than most headlines suggest.

Here are 10 evidence-based effects.

1. They Reduce Body Weight by 15 to 25% on Average

The STEP trials showed that semaglutide (2.4 mg weekly) produced average weight loss of 14.9% over 68 weeks. Tirzepatide performed even better in the SURMOUNT-1 trial, with participants losing up to 22.5% of their body weight at the highest dose. For a 200-pound person, that is 30 to 45 pounds. The weight loss occurs primarily through appetite suppression; GLP-1 drugs slow gastric emptying and act on brain regions that regulate hunger and satiety. This is not subtle appetite modification. Participants consistently report a dramatic reduction in food preoccupation and cravings.

2. They Lower Fasting Blood Sugar by 20 to 40 mg/dL in Diabetic Patients

GLP-1 drugs were originally designed to manage blood sugar, and they excel at it. They stimulate insulin secretion when blood sugar is elevated (not when it is normal, which reduces hypoglycemia risk), suppress glucagon release from the liver, and slow glucose absorption from meals. In the SUSTAIN trials, semaglutide reduced HbA1c by 1.5 to 1.8%, translating to roughly 30 to 40 mg/dL reduction in average blood sugar. Even in non-diabetic users, fasting glucose typically drops by 5 to 15 mg/dL.

Why it matters for your metabolic age: The blood sugar reduction from GLP-1 drugs can significantly lower your MetaAge score on Penlago. If you are using one of these medications, tracking your progress with the MetaAge calculator shows you the integrated metabolic benefit.

3. They Reduce Systolic Blood Pressure by 3 to 7 mmHg

GLP-1 drugs lower blood pressure through multiple mechanisms: weight loss reduces the physical load on the cardiovascular system, improved insulin sensitivity decreases sodium retention, and direct effects on blood vessel endothelium improve vascular function. A meta-analysis in Diabetes, Obesity and Metabolism found that semaglutide reduced systolic blood pressure by 4.7 mmHg on average. The effect is dose-dependent and tends to increase over the first 6 months of treatment.

4. They Shift Body Composition, but Not All Weight Lost Is Fat

This is an important nuance. While GLP-1 drugs produce impressive weight loss, approximately 25 to 40% of the weight lost is lean mass (muscle), according to body composition analyses from the STEP trials. Muscle loss is a concern because muscle tissue is your body’s primary glucose disposal site and a major contributor to basal metabolic rate. The clinical recommendation is to combine GLP-1 drugs with resistance training and adequate protein intake (1.0 to 1.2 grams per kilogram of body weight) to preserve lean mass during treatment.

Why it matters for your metabolic age: Muscle loss can partially offset the metabolic benefits of fat loss. Your MetaAge score captures the net effect through its blood sugar and BMI inputs.

5. They Reduce Visceral Fat More Than Subcutaneous Fat

Good news on the body composition front: GLP-1 drugs appear to preferentially target visceral fat, the metabolically dangerous kind that wraps around organs. A 2023 imaging study using MRI found that semaglutide reduced visceral adipose tissue by 30 to 40% in the first year. Since visceral fat is the primary driver of insulin resistance and metabolic inflammation, this targeted fat loss produces outsized metabolic benefits relative to total weight change.

6. They Improve Lipid Profiles Significantly

Beyond the three primary metabolic markers, GLP-1 drugs consistently improve cholesterol and triglyceride levels. Triglycerides typically drop by 15 to 25%, LDL cholesterol decreases by 5 to 10%, and HDL cholesterol increases slightly. A 2022 meta-analysis in Cardiovascular Diabetology found these lipid improvements occurred independently of weight loss, suggesting direct metabolic effects.

7. They Reduce Systemic Inflammation

GLP-1 drugs lower C-reactive protein (CRP) and other inflammatory markers by 20 to 40%, according to data from the SUSTAIN and STEP trial programs. This anti-inflammatory effect helps explain why these drugs reduce cardiovascular events even in people whose blood pressure and blood sugar improvements are modest. Inflammation is a shared driver of all three metabolic markers, so reducing it creates benefits that compound across metrics.

Why it matters for your metabolic age: The anti-inflammatory effect of GLP-1 drugs creates improvements that the MetaAge calculator captures across all three inputs simultaneously.

8. The Effects Reverse When You Stop the Medication

The STEP 1 extension trial showed that participants regained two-thirds of lost weight within one year of stopping semaglutide. Blood pressure and blood sugar levels also returned toward baseline. This does not mean the drugs are not valuable, but it does highlight the importance of building sustainable lifestyle habits alongside medication use. GLP-1 drugs can create a window of opportunity for establishing the exercise, dietary, and tracking habits that maintain metabolic health long-term.

9. They Cause Gastrointestinal Side Effects in Most Users

Nausea, vomiting, diarrhea, and constipation affect 40 to 70% of GLP-1 drug users, particularly during dose escalation. These side effects typically diminish over 4 to 8 weeks but can affect nutrition and hydration status during that period. Dehydration can temporarily raise blood pressure, and poor nutrition can impair blood sugar regulation. Gradual dose titration and adequate hydration help minimize these effects.

10. They Work Best as Part of a Comprehensive Metabolic Strategy

GLP-1 drugs are powerful but incomplete. The best outcomes in clinical trials came from participants who combined medication with exercise, dietary changes, and regular metabolic monitoring. A sub-analysis of the STEP trials found that participants who also exercised regularly lost 5% more weight and had better blood sugar improvements than those who relied on medication alone. The drugs lower the biological barriers to change, but lasting metabolic transformation still requires the fundamentals.

Why it matters for your metabolic age: Whether you are on a GLP-1 drug or not, tracking your MetaAge score on Penlago shows you the net effect of everything you are doing for your metabolic health.

Track Your GLP-1 Journey

If you are considering or already using a GLP-1 medication, the Penlago MetaAge calculator gives you a way to measure its integrated impact across blood pressure, blood sugar, and body composition. Check your metabolic age before starting, and recheck monthly to see the full trajectory.

Find out your metabolic age in 60 seconds – free at penlago.com.