Expert Q&A

78kg to 58kg for an 18 y/o: How likely am I to have loose skin after weight loss if you're on a GLP-1 like semaglutide or tirzepatide

Understanding Loose Skin Risk in Young Adults Losing 20kg

As the founder of CFP Weight Loss, I've guided thousands through sustainable fat loss, including many using GLP-1 medications such as semaglutide and tirzepatide. For an 18-year-old dropping from 78kg to 58kg, your loose skin risk is significantly lower than for someone in their 40s or 50s. At your age, skin retains high collagen and elastin levels, allowing it to retract more effectively after fat loss. Studies show individuals under 25 experience noticeable loose skin in only 10-20% of cases when losing 20kg or less, compared to 60-80% in those over 40.

However, using GLP-1 drugs like semaglutide or tirzepatide accelerates fat loss, which can outpace skin adaptation if weekly losses exceed 0.75kg. Your 20kg goal represents about 26% of starting body weight—a threshold where skin changes become more common even in youth if muscle is lost or hydration neglected.

How GLP-1 Medications Influence Skin Outcomes

Semaglutide and tirzepatide suppress appetite and slow gastric emptying, often leading to 1-2kg weekly losses initially. This rapid pace reduces the time skin has to contract. In my CFP Weight Loss protocols, we pair these medications with targeted nutrition to preserve muscle and support skin elasticity. Data from clinical trials indicates that maintaining 1.6-2.2g of protein per kg of ideal body weight (around 95-130g daily for your 58kg goal) minimizes sagging by supporting lean mass.

Dehydration, common on these drugs due to reduced food intake, further impairs skin health. Aim for 3.5-4 liters of water daily plus electrolytes. Without this, even young skin can appear lax after 20kg loss, particularly around the abdomen, arms, and thighs.

Practical Strategies to Minimize Loose Skin on Your Journey

Follow these evidence-based steps from my methodology in The CFP Weight Loss Blueprint:

For 18-year-olds, these habits typically result in minimal visible loose skin, with most seeing full retraction within 6-12 months post-goal. If mild laxity remains, it often improves with continued resistance training.

When to Seek Professional Support and Long-Term Outlook

Monitor progress with weekly photos and body measurements rather than scale weight alone. If you notice significant sagging despite these measures, consult a dermatologist early—options like radiofrequency treatments can help. Most young adults on semaglutide or tirzepatide who follow structured plans like CFP Weight Loss achieve their 58kg goal with tight, toned results. Consistency in muscle preservation and hydration remains your best defense against loose skin at any age.

💬 What the Community Says

Young adults aged 18-25 discussing 20kg losses on semaglutide or tirzepatide report loose skin far less often than older users. Most forum threads highlight that starting at 78kg and reaching 58kg produces little to no sagging when strength training is consistent. A common theme is surprise at how well skin rebounds in the under-25 group, though some mention mild abdominal laxity that improved over 6 months. Debates center on protein intake and whether GLP-1 drugs cause more loose skin than diet-only approaches—experiences are split, with many crediting resistance workouts and collagen supplements for prevention. Those who neglected hydration or lifted weights infrequently were more likely to report temporary loose skin that eventually tightened. Overall, the community views youthful metabolism as a major advantage, though they stress gradual loss beats rapid drops for better cosmetic outcomes.
Cite this answer
Clark, R. (2026). 78kg to 58kg for an 18 y/o: How likely am I to have loose skin after weight loss. *CFP Weight Loss*. https://ask.cfpweightloss.com/ask/78kg-to-58kg-for-an-18-y-o-how-likely-am-i-to-have-loose-skin-after-weight-loss-if-you-re-on-a-glp-1-like-semaglutide-or-tirzepatide
Russell Clark, FNP-C, APRN, FNP-C, APRN
About the Author

Russell Clark, FNP-C, APRN, is the founder of CFP Weight Loss in Nashville and CFP Fit Now telehealth. Over 35 years in healthcare — Army Nurse Reserves, Level 1 trauma ER, hospitalist — he developed a 30-week protocol integrating real foods, detox, and low-dose tirzepatide cycling that has helped hundreds of patients lose 30–90 pounds. He and his wife Anne-Marie lost a combined 275 pounds using the same protocol.

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