Diacylglycerol within whole meal intervention to reduce visceral fat,a randomized, double-blind, controlled study

INTERVENTION: Control Group (Middle‐aged and young adults):test meals using TAG as cooking oil;Trial Group (older adults):test meals using DAG as cooking oil;Control Group (older adults):test meals using TAG as cooking oil;Trial Group (Middle‐aged and young adults):test meals using DAG as cooking oil; CONDITION: Visceral fat obesity PRIMARY OUTCOME: Change in visceral fat area; SECONDARY OUTCOME: Gut Microbiota;Waist circumference;Lipidomics;body weight;hepatic steatosis;Metabolism‐Related Indicators; INCLUSION CRITERIA: 1.The elderly group consists of individuals aged 60–85, and the young and middle‐aged group consists of individuals aged 18–60. 2.Visceral fat area >= 80 cm^2. 3.Able to tolerate an oral diet. 4.Able to stand during body composition testing. 5.Able to consume the test meal. 6.Able to undergo blood sampling. 7.For the young and middle‐aged group, the participant must be able to sign the informed consent form. 8.For the elderly group, both the participant and a family member must sign the informed consent form;