Does Collagen Break a Fast? (By Fasting Goal)

Quick answer: Yes. A typical 10 g scoop of unflavored collagen peptides has about 35 calories and 9 g of protein, so it ends a fasted state. Some people still stir it into morning coffee as a “modified” fast for weight loss, but that’s a choice to shorten the true fast, not a loophole. If you’re fasting for autophagy or before a fasting blood test, wait until your eating window.

Try it yourself: On a 16:8 plan with meals from noon to 8 PM, collagen in your 8 AM coffee technically starts your eating window 4 hours early, turning 16:8 into 12:12. To keep the full fast, add collagen to your noon meal instead. Check your hours in the intermittent fasting calculator.

Calories and Protein in Collagen

Based on typical nutrition labels for unflavored collagen peptides (20 g serving: 70 calories, 18 g protein). Flavored products and “collagen creamers” often add sugar or fat, so check your label.

For comparison, black coffee has about 2 calories a cup, and a cup of bone broth has about 40 calories, putting collagen in the same range as broth. For the general rule, see how many calories break a fast.

Does Collagen Break a Fast? It Depends on Your Goal

Weight-loss intermittent fasting. Weight loss comes down to total intake over time. A 35-calorie scoop won’t undo that, and if it keeps you comfortable until lunch, it may help you stick with your plan. Just be honest about the clock: once you have collagen, you’re no longer fasting.

Autophagy. Autophagy is the body’s cell-recycling process. Lab research shows amino acids (the building blocks of protein) activate a cell-growth switch called mTOR, which turns autophagy down. A scoop of pure protein is a poor fit if autophagy is your goal. Most of this research is in cells and animals, there’s no simple test for autophagy in people, and no human study has tested collagen specifically.

Fasting blood tests. MedlinePlus advises plain water only for the 8 to 12 hours before most fasting tests, and says to tell your provider about any supplements you take.

What Does the Research Say About Collagen for Women?

Collagen is heavily marketed to women over 40 for skin and joints. The evidence is more mixed than the marketing.

• Skin. A 2025 meta-analysis of 23 randomized trials with 1,474 participants found that pooled results looked positive for hydration, elasticity and wrinkles. But when the authors split the studies, trials not funded by industry showed no benefit, and higher-quality trials showed no significant effect. The authors concluded there is currently no clinical evidence to support collagen for preventing or treating skin aging (Myung and Park, 2025). Supplement industry groups have disputed parts of the analysis.
• Joints. A 2019 meta-analysis of placebo-controlled trials in people with osteoarthritis found collagen lowered total symptom scores and pain ratings and improved stiffness, but it did not significantly improve the pain or physical-function subscales (García-Coronado et al., 2019). The authors themselves described collagen’s benefits for osteoarthritis as controversial, and these results apply to people with diagnosed joint disease, not to healthy joints.

Bottom line: collagen is a reasonable source of extra protein. Benefits for skin are unproven, and joint benefits are modest and uncertain.

Collagen, Fasting and Women Over 40

• Collagen isn’t a complete protein. Muscle loss speeds up with age, and fasting can make it harder to fit enough protein into fewer meals. An expert group (PROT-AGE) recommends adults over 65 aim for at least 1.0 to 1.2 g of protein per kilogram of body weight per day. Build meals around eggs, dairy, fish, poultry, beans or tofu, and treat collagen as an extra. Estimate your needs with the protein calculator for women.
• Timing. Taking collagen with your first meal keeps your fast intact and puts its protein where it counts.
• Medications and conditions. If you have kidney disease or have been told to limit protein, ask your doctor before adding protein powders of any kind.

If intermittent fasting has stalled in perimenopause, small calorie sources during the “fasting” hours are worth checking. Read why intermittent fasting may not be working in menopause.

Frequently Asked Questions

Can I take collagen while intermittent fasting?

Yes, but it ends the fast. Most people take it at the start of their eating window. Some use it in morning coffee as a modified fast for weight loss.

Does collagen break autophagy?

Probably. It’s almost pure protein, and amino acids switch on mTOR, which slows autophagy in lab studies. There’s no human research on collagen and autophagy.

Does collagen in coffee break a fast?

Yes. A scoop adds about 35 calories and 9 g of protein to otherwise near-zero-calorie black coffee.

Will collagen kick me out of ketosis?

Unlikely. Unflavored collagen peptides contain little or no carbohydrate. Flavored versions may contain sugar.

When is the best time to take collagen if I’m fasting?

With your first meal. There’s no evidence that taking it on an empty stomach works better.

Does creatine break a fast too?

Plain creatine has essentially no calories. See does creatine break a fast and does MCT oil break a fast.

Related Tools

• Intermittent Fasting Calculator
• Protein Calculator for Women
• Do Electrolytes Break a Fast?
• Does Salt Break a Fast?

This article is for general information only and is not medical advice. Read our Medical Disclaimer.

Sources

• Myung SK, Park Y. Effects of Collagen Supplements on Skin Aging: A Systematic Review and Meta-Analysis of Randomized Controlled Trials. Am J Med. 2025 — https://doi.org/10.1016/j.amjmed.2025.04.034
• García-Coronado JM, et al. Effect of collagen supplementation on osteoarthritis symptoms: a meta-analysis of randomized placebo-controlled trials. Int Orthop. 2019 — https://pubmed.ncbi.nlm.nih.gov/30368550/
• Liu C, et al. Functional Amino Acids and Autophagy: Diverse Signal Transduction and Application. Int J Mol Sci. 2021 — https://pmc.ncbi.nlm.nih.gov/articles/PMC8592284/
• Bauer J, et al. Evidence-based recommendations for optimal dietary protein intake in older people: a position paper from the PROT-AGE Study Group. J Am Med Dir Assoc. 2013 — https://doi.org/10.1016/j.jamda.2013.05.021
• MedlinePlus (NIH): Fasting for a Blood Test — https://medlineplus.gov/lab-tests/fasting-for-a-blood-test