The “calories in, calories out” formula for weight loss success is a myth because it oversimplifies the complex process of calculating energy intake and expenditure. More importantly, it fails to consider the mechanisms our bodies trigger to counteract a reduction in energy intake.
So while you may achieve short-term weight loss following the formula, you’ll likely regain it.
What’s more, calorie counting can do more harm than good, taking the pleasure out of eating and contributing to developing an unhealthy relationship with food. That can make it even harder to achieve and maintain a healthy weight.
For long term weight loss, it’s important to follow evidence-based programs from health-care professionals and make gradual changes to your lifestyle to ensure you form habits that last a lifetime.
Excessive calories are bad for you.
Every one needs calories. Avoiding fats and oils means you turn to carbohydrates and sugars, both of which have a higher glycemic index.
There’s a reason the US has demonised fat for decades and over those same decades the obesity epidemic has only gotten worse.
Also, the calories in; calories out approach is a myth and probably not good for you long term:
https://www.sydney.edu.au/news-opinion/news/2023/07/05/its-time-to-bust-the-calories-in-calories-out-weight-loss-myth.html