Hello LAAnimeGuy and welcome to the forum.
If it makes you feel better, you’ve mis-interpreted information. You don’t need to exercise for 90 minutes to burn off all of what you’ve eaten in order to lose weight. However, you need to consume far more calories than you currently do.
Don’t be alarmed, since all shall hopefully become clearer.
Even its resting state, you still expend calories, as your body’s various systems require energy in order to maintain your existence. You may have heard the term BMR (basal metabolic rate). Your BMR is roughly how many calories your body requires to conduct the things you don’t even give a second thought towards, ie keeping your heart pumping blood and organs functioning as they should.
When you throw activity into equation, your body requires a higher amount of calories. The amount of additional calories required on top of your BMR varies, depending upon how strenuous the level of activity. In order to provide your body with sufficient calories that meets its energy demand, one’s TDEE (total daily energy expenditure) should be also obtained.
To obtain both your BMR and TDEE, you should research BMR calculators, since they’re largely accurate in determining both, based upon you current statistics and level of activity.
If you’d not already guessed, in order to expend the energy stored in excess fat, you need to introduce a daily calorie deficit between your TDEE and BMR.
Let’s say, for example, based upon your measurements your BMR is 1800Kcal and your TDEE is 2300Kcal. The figure between the two allows you to introduce a daily calorie deficit of around 400-500Kcal.
By introducing a daily deficit, in order to provide your body with sufficient energy to fuel your level of activity, your body turns to the excess energy stored in the fat that you possess. As such, by turning to stored fat, you begin to lose weight.
Granted, a daily deficit of 500Kcal, combined with your level of activity, may only net you a weekly loss of around 3lbs. However, when you consider that approximately 10,000Kcal will have been expended in order to achieve such a goal, a consistent weekly reduction of 3lbs soon begins to add up.
Moreover, it’s a far more sensible and sustainable route towards maintaining the level of loss, once your goal weight has been reached.
In order to ensure that you don’t plateau, re-evaluate both your BMR and TDEE. On the assumption that your level of activity remains the same, with each stone lost, your body will require approximately 100 fewer daily calories.
Whilst your existing diet isn’t poor at all, in order to begin witnessing the kind of weight loss you desire, you need to increase your consumption, so that it meets your BMR. Failure to do so will lead to your body eventually holding on to the excess that you’re so desperate to lose, since you simply aren’t providing it with sufficient calories.
Consider introducing unsalted nuts (both healthy and energy dense) as well as whey protein shakes into your diet, as means of increasing your calorie intake. With your evening meal, also consider including a mix of roasted sweet potato and Mediterranean veg upon the side.
Homemade sauces, made with chopped/crushed tomatoes, infused with garlic, chilli (optional), oregano, a small tin of tomato puree and basil, alongside a tablespoon of brown sugar also provide a wonderful accompaniment to both fish and chicken. Don’t worry about the tablespoon of sugar, since it’s insignificant, largely since the contents of a simmering pan of tomato sauce will yield 2-3 servings; it’s simply added to reduce the tartness of the tomato.
To conclude, success in achieving weight loss and maintaining it, once a goal weight is reached, is very much a game of numbers. Once you know what those numbers are, based upon your current stats and level of activity, you stand a far greater chance of success.