Diets are marketed on their differences. Compare the actual instructions and a large area of overlap appears, which explains why trials comparing them tend to find modest differences in outcome.
The shared instruction set
Whatever the stated theory, most structured plans end up telling a follower to eat more vegetables, more whole foods and more protein, and to eat fewer packaged products.
Low-carbohydrate plans remove sweets, refined bread and sugary drinks. Low-fat plans remove fried food, pastry and many snacks. The excluded lists differ but they intersect heavily.
What both remove is the category of cheap, energy-dense, highly palatable products that is easiest to overeat, and that removal does much of the work either way.
Restriction operates through attention
Any rule that requires checking what a food contains slows eating down and introduces a decision point where none existed. Some foods fail the check and are not eaten.
The rule itself need not be metabolically meaningful for this to reduce intake. It only needs to be specific enough to interrupt automatic consumption.
Which is part of why unrelated plans produce comparable early results, and why those results fade as the rules become habitual and stop interrupting anything.
Where genuine differences sit
Real differences do exist between approaches, mostly in how quickly weight is lost at the start and in how satisfied people feel while following them.
Very low carbohydrate intake produces rapid early loss largely through water, because stored carbohydrate is held with water and both leave together.
Higher protein and higher fibre intakes are consistently associated with greater fullness for the same energy, which affects how sustainable a plan feels rather than how it works chemically.
Adherence outranks composition
Comparative trials repeatedly find that the difference between people following the same diet is larger than the difference between the diets themselves.
That points to adherence as the dominant variable. A plan followed loosely for years beats an optimal plan abandoned within weeks.
Which reframes the choice: the useful question is which set of rules a particular person can live inside, not which set is theoretically superior.
The strong claims are the weakest part
Plans built on a single mechanism, whether insulin, inflammation or acidity, tend to overstate one pathway and ignore the several others operating at the same time.
The elaborate rationale is often doing marketing work rather than physiological work, since the practical instructions would be similar without it.
Anyone with diabetes, kidney disease or a history of disordered eating should set dietary changes with a clinician, because the general logic above does not hold in those situations.