From the PLOS paper >To assist in complying with diet recommendations, participants in the diet change group each received a small hamper of food items including olive oil (Cobram Estate), natural nut butter (Mayvers), nuts and seeds (walnuts, almonds, pepitas, sunflower seeds) and spices (cinnamon, turmeric). They were told to keep their shopping receipts in order to receive a $60 gift card as reimbursement for study foods. Participants in the diet change group also received a brief, 5-minute phone call on Day 7, Day 14 to ask if they were having any difficulties adhering to the diet and troubleshoot problems with reference to the prescribed handouts. Participants in the habitual diet group were given no instructions regarding diet, and were simply asked to return after 3 weeks for follow up.
https://journals.plos.org/plosone/article?id=10.1371/journal...So if you enroll subjects in a study, give them attention, free food, gift card, phone calls, etc. then after three weeks they will feel less depressed than a group of subjects for which nothing was done.
It would be more convincing if they had a third group that they fed blue cheese bacon cheeseburgers, french fries, diet Coke and Lil Debbie cakes from a convenience store. I'd bet even money that the third group would have been less depressed too.
So if you enroll subjects in a study, give them attention, free food, gift card, phone calls, etc. then after three weeks they will feel less depressed than a group of subjects for which nothing was done.
It would be more convincing if they had a third group that they fed blue cheese bacon cheeseburgers, french fries, diet Coke and Lil Debbie cakes from a convenience store. I'd bet even money that the third group would have been less depressed too.