Document and Entity Information - shares
 3 Months Ended
Mar. 29, 2020
May 22, 2020
Document And Entity Information    
Entity Registrant Name Fat Brands, Inc  
Entity Central Index Key 0001705012  
Document Type 10-Q  
Document Period End Date Mar. 29, 2020  
Amendment Flag false  
Current Fiscal Year End Date --12-27  
Entity Current Reporting Status Yes  
Entity Interactive Data Current Yes  
Entity Filer Category Non-accelerated Filer  
Entity Small Business Flag true  
Entity Emerging Growth Company true  
Entity Ex Transition Period true  
Entity Shell Company false  
Entity Common Stock, Shares Outstanding   11,894,895
Document Fiscal Period Focus Q1  
Document Fiscal Year Focus 2020