✪ Key Highlight: Four weeks of alternate-day fasting causes significant muscle loss that protein supplements cannot prevent, new research confirms.
Introduction
Alternate-day fasting promises quick weight loss without counting calories every single day.
But new research published in the journal Nutrients reveals a serious problem that most people never consider before starting this popular diet.
Hi, I’m Abdur, your nutrition coach and today I’m going to analyze the troubling discovery that alternate-day fasting causes measurable muscle loss even when people add protein supplements to their fasting days.
What Exactly Is Alternate-Day Fasting And Why Do People Try It?
Alternate-day fasting is a specific type of intermittent fasting that involves switching between feeding days and fasting days every 24 hours.
Unlike other fasting methods that restrict eating to certain hours each day, alternate-day fasting allows people to eat freely one day and then consume only 400 to 600 calories the next day.
This approach has gained popularity because it seems simpler than counting calories every single day.
The numbers behind obesity make it clear why people desperately search for effective weight loss strategies that actually work.
Around 44 percent of adults worldwide are overweight and 16 percent are obese, while in Singapore specifically, approximately 41 percent are overweight and 14 percent are obese.
Previous research suggested that alternate-day fasting could decrease body mass, fat mass, body mass index, cholesterol levels, blood pressure, and triglyceride levels.
These potential benefits made alternate-day fasting seem like an attractive option for people concerned about their overall health and metabolic markers.
✪ Fact: Intermittent fasting has attracted attention from researchers worldwide due to its potential benefits on metabolic and cardiovascular health markers.
How Did Researchers Study The Effects Of Alternate-Day Fasting?
Scientists designed two separate studies to answer important questions about alternate-day fasting and muscle preservation.
Both studies enrolled young Asian males aged 21 to 35 years with a body mass index greater than 23 kilograms per square meter who did not smoke or use tobacco products.
Researchers excluded individuals taking long-term medications, those with health conditions that might be aggravated by fasting, or those unable to meet the diet and physical activity requirements.
The first study subjected 20 participants to a four-week alternate-day fasting protocol that began at 12 AM, alternating between fasting and feeding days in 24-hour cycles.
On fasting days, participants could only consume water or zero-calorie beverages and a small meal of 400 to 600 calories between 12:00 PM and 2:00 PM.
On feeding days, free intake of foods and beverages was permitted, giving people flexibility in what they ate when they were not fasting.
The second study took the research one step further by investigating whether increasing protein intake would help preserve muscle during weight loss with 26 participants divided into two groups.
✪ Note: Body composition was measured using bioelectrical impedance analysis, a technology that accurately assesses muscle and fat tissue throughout the body.
What Did The Research Reveal About Muscle Loss During Fasting?
The results painted a clear and concerning picture of what happens to the body during alternate-day fasting.
All body composition measures showed significant reductions after the four-week intervention, including body mass, fat mass, and fat-free mass.
Fat-free mass is the scientific term for muscle tissue, and its reduction means people were losing muscle along with fat.
Physical activity levels were significantly lower at the end of weeks 2 and 3 compared to baseline measurements, suggesting that people felt weaker as they lost muscle.
During fasting days, Study 1 subjects consumed an average of 525 calories, of which 38 percent, 37 percent, and 25 percent came from carbohydrates, fat, and protein respectively.
The protein group in Study 2 consumed 495 calories on fasting days, of which 34 percent, 26 percent, and 40 percent came from carbohydrates, fat, and protein respectively.
The most important discovery was that low-dose protein supplementation proved insufficient for muscle preservation during alternate-day fasting, even though the protein group consumed more protein than the control group.
✪ Pro Tip: Monitor your strength levels and physical performance during any fasting protocol as early warning signs of muscle loss.
Why Did Protein Supplements Fail To Protect Muscle?
The protein group consumed a 25-gram whey protein supplement containing 125 calories during their fasting days.
This amount of protein sounds reasonable, but the study revealed several critical problems with this approach.
Fasting-day protein intake remained below the recommended daily levels even with supplementation, meaning people were not getting enough protein to maintain their muscle tissue.
The differences in total protein intake between the protein group and control group were actually quite small when you consider protein consumed across both fasting and feeding days.
Researchers did not monitor feeding-day protein intake during the study, which means participants might have eaten less protein on their feeding days without realizing it.
Your body needs adequate protein every single day to maintain muscle tissue, not just on fasting days.
The researchers concluded that short-term alternate-day fasting resulted in significant reductions in body mass, fat mass, and fat-free mass, with increasing protein intake through low-dose whey protein supplementation failing to mitigate muscle loss.
✪ Fact: Your muscles require consistent daily protein intake to maintain their structure and function, regardless of your fasting schedule.
What Should People Do To Prevent Muscle Loss While Fasting?
The researchers suggested that future studies should investigate protein or leucine supplementation during both fasting and feeding days, combined with resistance training.
Leucine is an essential amino acid that plays a crucial role in muscle protein synthesis, the process your body uses to build and maintain muscle tissue.
This recommendation highlights an important insight that if you want to preserve muscle during weight loss, you need a comprehensive strategy that includes adequate protein, specific amino acids, and strength training.
Simply adding a protein shake on fasting days will not be enough to protect your muscle mass from the effects of severe calorie restriction.
Resistance training sends a powerful signal to your body that you need to keep your muscle tissue, which can help counteract the muscle-wasting effects of fasting.
You also need to ensure adequate protein intake across all days of the week, not just during fasting periods, to give your body the building blocks it needs for muscle maintenance.
The study also noted that diastolic blood pressure and fasting blood glucose showed some changes, but these effects were short-lived and did not persist throughout the entire study period.
✪ Pro Tip: Combine any fasting protocol with regular resistance training at least three times per week to signal your body to preserve muscle tissue.
The Bottom Line
Alternate-day fasting can help you lose weight quickly, but the research clearly shows that you will lose muscle along with fat unless you take specific protective measures.
Quick weight loss means nothing if you sacrifice the muscle that keeps you strong, healthy, and metabolically active for life.
I would love to hear your thoughts about this research and whether you have tried alternate-day fasting yourself, so please share your questions or experiences in the comment section below.
References
At NutritionCrown, we use quality and credible sources to ensure our content is accurate and trustworthy. Below are the sources referenced in writing this article:
- News Medical: Alternate-day fasting cuts body fat but also reduces muscle
- UH Cancer Center: Intermittent fasting study find dieters shed muscle not fat
- Ole Miss: Time-Restricted Eating Study
- The Journal of Clinical Endocrinology & Metabolism: Time-restricted eating study research
- PubMed: Alternate-day fasting research study
