When it comes to diet, quality matters
While weight loss does, to a large degree, come down to a caloric deficit, there are few major caveats to this rule. First, not all calories are created equal, because foods affect the body differently. For instance, a 400-calorie bagel eaten first thing in the morning spikes your insulin levels and causes a sugar crash a few hours later. Not only will you be dragging, you’ll also be famished—making it harder to adhere to your daily calorie goal. Never mind the fact that carbohydrates also get stored as fat.
Diets do not work all the same
If calories were all that mattered, all diets would work equally well. But different diets with the same calorie goals can lead to different weight loss results. For instance, a 1,500 calorie-a-day Paleo diet doesn’t necessarily yield the same effects as a 1,500 calorie-a-day Ornish diet.
As for low-carb diets (far fewer bagels), which are typically high in protein, you may lose a significant amount of weight then hit a wall and experience trouble meeting your long-term weight loss goals. The culprit? The onset of inflammation due to excess protein.