Acquisitions - Additional Information (Detail) - USD ($) $ / shares in Units, shares in Thousands												3 Months Ended		12 Months Ended
	Aug. 17, 2023	Apr. 10, 2023	Apr. 03, 2023	Feb. 17, 2023	Oct. 03, 2022	Aug. 22, 2022	Feb. 18, 2022	Dec. 21, 2021	Aug. 16, 2021	Jul. 30, 2021	Mar. 22, 2021	Jul. 01, 2023	Apr. 01, 2023	Dec. 30, 2023	Dec. 31, 2022	Jan. 01, 2022
Business Acquisition [Line Items]
Goodwill														$ 243,441,000	$ 155,998,000	$ 157,374,000
Business acquisition, purchase price allocation, tax asset valuation allowance														89,801,000	$ 35,818,000
Denross Limited
Business Acquisition [Line Items]
Business acquisition, aggregate purchase price							$ 4,500,000
Business acquisition, cash payment				$ 375,000			3,100,000	$ 650,000
Business acquisition, cash in reserves							750,000
Business acquisition, purchase price allocation, assumed liabilities							166,000
Business acquisition, purchase price allocation, cash							4,000
Goodwill							4,645,000
Business acquisition, purchase price allocation, deferred tax asset							496,000
Business acquisition, purchase price allocation, tax asset valuation allowance							496,000
Business acquisition, purchase price allocation, other receivables							3,000
Denross Limited | Customer Relationship
Business Acquisition [Line Items]
Business acquisition, purchase price allocation, finite lived intangible assets							14,000
Checkweight Limited
Business Acquisition [Line Items]
Business acquisition, aggregate purchase price							1,500,000
Business acquisition, cash payment				$ 125,000			1,250,000
Business acquisition, cash in reserves							250,000
Business acquisition, purchase price allocation, assumed liabilities							56,000
Business acquisition, purchase price allocation, cash							4,000
Goodwill							1,291,000
Business acquisition, purchase price allocation, deferred tax asset							5,000
Business acquisition, purchase price allocation, tax asset valuation allowance							5,000
Business acquisition, purchase price allocation, other receivables							4,000
Checkweight Limited | Franchise Rights Acquired
Business Acquisition [Line Items]
Business acquisition, purchase price allocation, finite lived intangible assets							240,000
Checkweight Limited | Customer Relationship
Business Acquisition [Line Items]
Business acquisition, purchase price allocation, finite lived intangible assets							$ 17,000
Weight Watchers of Maine, Inc.
Business Acquisition [Line Items]
Business acquisition, aggregate purchase price									$ 2,250,000
Business acquisition, cash payment	$ 112,500					$ 112,500			1,999,000
Business acquisition, cash in reserves									225,000
Business acquisition, assumed net liabilities									26,000
Goodwill									2,153,000
Weight Watchers of Maine, Inc. | Franchise Rights Acquired
Business Acquisition [Line Items]
Business acquisition, purchase price allocation, finite lived intangible assets									41,000
Weight Watchers of Maine, Inc. | Customer Relationship
Business Acquisition [Line Items]
Business acquisition, purchase price allocation, finite lived intangible assets									$ 56,000
The WW Group, Inc.
Business Acquisition [Line Items]
Business acquisition, aggregate purchase price											$ 17,500,000
Business acquisition, cash payment					$ 2,300,000					$ 6,450,000	8,255,000
Business acquisition, cash in reserves											2,300,000
Business acquisition, assumed net liabilities											495,000
Business acquisition, purchase price allocation, inventories											162,000
Business acquisition, purchase price allocation, property and equipment											41,000
Business acquisition, purchase price allocation, other assets											4,000
The WW Group, Inc. | Franchise Rights Acquired
Business Acquisition [Line Items]
Business acquisition, purchase price allocation, indefinite lived intangible assets											16,885,000
The WW Group, Inc. | Customer Relationship
Business Acquisition [Line Items]
Business acquisition, purchase price allocation, finite lived intangible assets											408,000
The WW Group Co.
Business Acquisition [Line Items]
Business acquisition, aggregate purchase price											3,114,000
Business acquisition, cash payment			$ 599,000								2,605,000
Business acquisition, cash in reserves											599,000
Business acquisition, assumed net assets											90,000
Business acquisition, purchase price allocation, inventories											6,000
Business acquisition, purchase price allocation, property and equipment											25,000
Business acquisition, purchase price allocation, other assets											1,000
The WW Group Co. | Franchise Rights Acquired
Business Acquisition [Line Items]
Business acquisition, purchase price allocation, indefinite lived intangible assets											3,040,000
The WW Group Co. | Customer Relationship
Business Acquisition [Line Items]
Business acquisition, purchase price allocation, finite lived intangible assets											$ 42,000
Weekend Health, Inc. d/b/a Sequence
Business Acquisition [Line Items]
Business acquisition effective date		Apr. 10, 2023
Business acquisition, aggregate purchase price		$ 132,000,000
Business acquisition, cash payment		64,217,000
Business acquisition, purchase price allocation, cash		25,800,000
Business acquisition, amount to be paid one year from closing date		16,000,000
Business acquisition, amount to be paid two years from closing date		16,000,000
Transaction related costs												$ 4,886,000	$ 3,719,000	8,605,000
Total revenue														30,542,000
Net loss														5,477,000
Goodwill														$ 89,742,000
Weekend Health, Inc. d/b/a Sequence | Common Stock
Business Acquisition [Line Items]
Business acquisition, equity interest issued as consideration for acquisition, value		$ 34,702,000
Business acquisition, equity interest issued as consideration for acquisition, shares		7,996
Business acquisition, common stock price per share		$ 4.34