It's because people crave and store fats when they have fat soluble vitamin deficiencies. A lot of people have a vitamin k deficiency, vitamin e deficiency, plus other fat soluble vitamins. Over time, these deficiencies lead to various issues, esp autoimmune ones. It isn't per se due to being fat, it is because they are deficient and out of balance. But we don't try to give them vitamins, we fucking starve them as punishment for being fat, making the deficiency much worse, and wonder why they can't maintain a diet or weight loss lol
Before you even start to argue against the idea that fat soluble vitamins play a role in autoimmune disease, obesity related diseases, etc, here are some studies on Type 2 diabetes and fat soluble vitamins:
"Vitamin A: a missing link in diabetes?" https://pmc.ncbi.nlm.nih.gov/articles/PMC4623591/
"Association of plasma vitamin A level with type 2 diabetes mellitus: a community aging population-based cross-sectional study" "Totally, our data indicated the modifying effect of circulating lipids on the relationship between VA and T2DM. That might partly explain the discrepant conclusions in different studies regarding the association between VA nutritional status and the risk of T2DM" https://www.sciencedirect.com/science/article/pii/S2213453024000909
"Combined effect of high-dose vitamin A, vitamin E supplementation, and zinc on adult patients with diabetes: A randomized trial" https://www.sciencedirect.com/science/article/pii/S2090123220301223
"Effect of vitamin E intake on glycemic control and insulin resistance in diabetic patients: an updated systematic review and meta-analysis of randomized controlled trials" "We found that vitamin E intake significantly reduces levels of HbA1c, fasting insulin, and HOMA-IR in diabetic patients, particularly patients with T2DM. Also, a significant reducing effect of vitamin E intake on fasting blood glucose was found in studies with an intervention duration of < 10 weeks" https://nutritionj.biomedcentral.com/articles/10.1186/s12937-023-00840-1
"Does Vitamin D Have a Role in Diabetes?" "Although the function of vitamin D in regulating blood glucose is still not fully understood, vitamin D status appears to play a role in the onset and management of diabetes mellitus" https://pmc.ncbi.nlm.nih.gov/articles/PMC9671203/
"What is the impact of vitamin D supplementation on glycemic control in people with type-2 diabetes: a systematic review and meta-analysis of randomized controlled trails" https://bmcendocrdisord.biomedcentral.com/articles/10.1186/s12902-022-01209-x
"Effect of vitamin K2 on type 2 diabetes mellitus: A review" "Studies showed vitamin K2 intake reduced 7% T2DM risk with each 10-μg increment" https://www.diabetesresearchclinicalpractice.com/article/S0168-8227(17)31256-1/abstract
"Vitamin K2 supplementation improves impaired glycemic homeostasis and insulin sensitivity for type 2 diabetes through gut microbiome and fecal metabolites" https://bmcmedicine.biomedcentral.com/articles/10.1186/s12916-023-02880-0
"Beneficial Effects of Vitamin K Status on Glycemic Regulation and Diabetes Mellitus: A Mini-Review" https://www.mdpi.com/2072-6643/12/8/2485
"Effects of coenzyme Q10 supplementation on glycemic control: A GRADE-assessed systematic review and dose-response meta-analysis of randomized controlled trials" "CoQ10 supplementation has beneficial effects on glycemic control, especially in diabetes" https://www.thelancet.com/journals/eclinm/article/PIIS2589-5370(22)00332-7/fulltext