Hard to say. It will make a big difference if you are insulin resistant or insulin sensative.

To access body fat for energy (to burn body fat), insulin has to be low.

There are three categories of macro nutrients. Carbohydrates, fat and protein.

Carbohydrates raise insulin levels. Fat does not raise insulin levels to speak of. Protein depends on the fed state. If eaten with carbohydrates it will raise insulin modestly. In the absence of carbs it has a minimal insulin effect.

So if a person is trying to access stored groceries (body fat) to utilize it for energy it requires that insulin levels be low. The best way to accomplish low insulin levels is to not eat foods that spike it higher. Bread will definitely do that. So toast for breakfast is not the best choice. But if that is the only carbohydrate you eat and the rest of the day is mostly protein and fat then you might still lose weight. It is just hard to say.

But if you would substitute something like chaffles (made from eggs and cheese) for the toast, it would help keep your insulin levels lower at breakfast, helping with the weight loss.

You can lose weight by restricting calories enough, but calorie restriction diets make a person hungry all the time. A low carb or ketogenic diet allows a person to eat to satiation, therefore not being hungry, by just avoiding certain high carbohydrate foods (like bread, poataoes, etc.).

The other key to keeping insulin levels low is to limit meals to two or three a day with no snacks in between. If snacks must be eaten make them fat/protein rather than carbohydrates. Low insulin levels are the key to accessing body fat for energy. Accessing body fat for energy is the way fat loss weight happens. The easiest way to lower insulin is to not eat the foods that raise insulin. The foods that raise insulin are carbohydrates. Insulin can also be lowered by reducing calories enough, but it is much harder to maintain such a diet because of the hunger factor. Calorie restriction diets also lower basal metabolism, which is counter productive for weight loss.

I'm not a doctor nor nutritionists. This is not medical or dietary advice. Just the way it is as I understand it. Do your own due diligence.

https://www.youtube.com/watch?v=xwKmVjSXTDk&list=PL48jnTudSMf_4z7qfiymmOf-xbYJJUSDX

John