Sounds like advice to limit magnesium, not take supplements
‘The team began by asking how magnesium shapes metabolism—the way cells make and burn energy called ATP. Magnesium is the body’s fourth-most abundant charged mineral, vital for blood sugar control, blood pressure, and bone strength. Yet the scientists discovered that an excess of magnesium inside mitochondria, the cell’s “power plants,” actually slows energy production.And …”
And I'm guessing that a junk food diet is not high in Mg and therefore the excess Mg in the mitochondria is due to metabolism issues from being obese, not from food intake or MG intake.