You can just go on a calorie deficit and it will reduce your visceral fat when you start getting lean enough.
But obviously, most people are a lot more interested in finding a magic food which does this rather than a proven calorie deficit, which is highly effective.
To do it right it requires quite an effort to no go too much into calorie deficit.
It definitely is not "you can just go on a calorie deficit", that is how jo-jo effect works.
For average person that has children, full time job, and whole range of adult responsibilities it is hard. Not impossible but hard, this is why people are looking fo easier solutions.
Why not, though? Eating is fun and pleasurable. If we can figure out a way to eat the things that we want, in the quantities that we want, while maintaining our health, why shouldn't we try?
I've lost weight through forcing myself into a calorie deficit, and it works really well, but it's not particularly fun.
Abstention is commercially a no go zone, eating 'different' is a goldmine. It is why 'going on a diet' in the 1970's still meant eating less, while starting in the 1980's the phrase was turned into just eating the latest industry fad miracle food.
You can induce a calorie deficit by eating foods that fill you up but don’t have many calories. Also avoiding the sugar-spike carbs cause leaving you even hungrier shortly after works also.
A good dietician is worth a few consults if you don’t have the will power to just fast. And as a bonus you don’t lose muscle mass as well because they’ll focus on keeping protein up.
The vast majority of people who lose weight by calorie restriction gain it back, so I wouldn't call it highly effective. Short term yes, but long term, definitely not.
> which is highly effective
How are you defining highly effective? In the sense that a body will definitely lose weight when starved? Or in the sense that counting calories is broadly effective as a weight loss strategy?
The former is painfully obvious and entirely unhelpful, and the latter is provably false.
> highly effective
Purely behavioral lifestyle interventions have the lowest long term success rates of all available treatments for obesity. It's especially unreliable if you have weight loss targets higher than 15%.
They are of course still widely recommended due to numerous benefits other than weight loss, but "highly effective" is just wrong in the context of obesity treatments.