What happens when mice can't use a special fasting hormone?
Fibroblast Growth Factor 21-Null Mice Do Not Exhibit an Impaired Response to Fasting
Not medical advice. For informational purposes only. Always consult a healthcare professional. Terms
Surprising Findings
Blocking FGF21 signaling had no major effect on blood glucose, ketones, or fatty acids during fasting.
FGF21 is strongly induced during fasting and widely believed to be central to metabolic adaptation—yet removing it didn’t break the system.
Practical Takeaways
Don’t assume your fasting results depend on one 'magic' hormone—your body has redundancy built in.
Not medical advice. For informational purposes only. Always consult a healthcare professional. Terms
Surprising Findings
Blocking FGF21 signaling had no major effect on blood glucose, ketones, or fatty acids during fasting.
FGF21 is strongly induced during fasting and widely believed to be central to metabolic adaptation—yet removing it didn’t break the system.
Practical Takeaways
Don’t assume your fasting results depend on one 'magic' hormone—your body has redundancy built in.
Publication
Journal
Frontiers in Endocrinology
Year
2016
Authors
P. Antonellis, M. Hayes, A. Adams
Related Content
Claims (5)
When mice don't have a certain protein called FGF21, their liver doesn't turn on some sugar-making genes as much and can't make as much glucose from raw materials after fasting — but their blood sugar still stays normal, probably because other systems step in to help.
When scientists turned off the FGF21 gene in mice, the mice still handled fasting just fine — their blood sugar, insulin, and energy levels stayed normal, even though a few liver genes acted a little differently.
Blocking a hormone called FGF21 in fasting mice doesn’t really change their blood sugar, energy levels, or liver fuel stores — meaning this hormone might not be essential for how their bodies adapt to not eating for a short time.
In mice, a hormone called FGF21 helps turn on liver genes that burn fat and make sugar when food is scarce — without it, those genes don’t turn on as much.
When mice don't have enough of a protein called FGF21 during fasting, their livers store more fat because they burn less fat and take in more from the blood — but this doesn't affect how the body overall uses energy.