Needing to know if this will work?

Depends on your height and activity level I guess... What do you have your weight loss goal set to in MFP? For losing that amount, 1lb per week or less would be a good target - it might not be as fast as you'd like, but you will get there eventually!

Make sure your daily calorie goal is appropriate, and do your best to stick to it but don't beat yourself up if you go over occasionally. We're all human! Include some snacks, sweets or whatever if you like that sort of thing, but keep your portions reasonable and log it all. Some people (myself included!) feel deprived if they're "not allowed" to have particular foods, so I prefer not to have anything off limits. Others struggle to moderate and find it best to avoid certain things until they get their eating under control, and that's fine too! We all need to find the method that works best for us.

Exercise is great and will help your overall health and fitness, but although you can create your deficit through exercise most people find it easier to do that by eating less. So make your calorie goal your focus, and eat back a portion of your exercise calories too. Monitor your weight changes and adjust your intake as necessary, since everything (both food and exercise burns) is an estimate anyway.

How long have you been eating 1400 calories, and how do you feel on it? If you're finding it difficult then it might just take a while to get used to eating less, but if you've been at this a while then it may be that your goal is too aggressive and you could slow it down to give yourself a bigger allowance. Definitely get a food scale if you don't already have one, and weigh or measure everything you eat for accuracy in logging. Don't forget drinks, sauces, oils and condiments too!

Finally, don't worry if your weight bounces around a bit - fluctuations are normal, especially for women, so just look at the overall trend over the course of several weeks or months.

You've got this - good luck!

Hi OP remember not to just go on weight, but also by how you look and feel. Your weight might not change a huge amount once you start toning up. You also don't say what your hiits are, cardio or weights? Do both. Also, is 3 times a week more than usual for you or normal? If you're not following a plan that changes after a few weeks, make sure to change something in your workout routine, weights/intensity/timing/cardiomachine. YOur body will adapt quite quickly to what you are doing so if you don't change one of the above after a few weeks you'll not be pushing yourself and won't see as much progress. Don't push it though, if the hiits/particular exercise is new to you and you're not in a class or with a PT then up your progress slowly to avoid injury. If you know what you're doing then... you know how hard to go