A very low-fat diet will work. The Randle Cycle explains how we metabolize fats or sugar efficiently but not both at once. Eating fat and carbs together (a "mixed" or "balanced" diet) leads to fat storage (high triglycerides) and other metabolic problems. So yes, you can certainly lose a great deal of weight eating a VERY low fat diet, but it's nutritionally lacking and difficult to sustain. Or, you can eat a very low carb diet (high fat) such as keto or carnivore. Having done both, I feel keto is much easier than all fruit, veg, grains, partly because I eat two meals and am satisfied. But also because all my health markers improve dramatically.