How to firm up the belly? And what exactly does it mean to firm your belly? Well, every time we talk about “firming” we are talking indirectly about muscle toning. So, if we want to firm up the legs, butt, arms and yes, even the belly, the best thing is to combine the diet with physical exercise. Now, if we want to firm up the stomach, there are two other things to take into consideration : the first is that a swollen stomach, even though a trained abdominal wall may have, will never seem as firm and toned as we want it, so we will have to pay attention to identify the foods that inflate us the most, and try to limit them, also choosing to eat meals that maybe don’t weigh us down too much if we have digestive difficulties.The second is that even a little abdominal fat is enough to reduce the effect of a toned stomach. So to firm the belly we will have to reduce fat (with the right calorie deficit) and abdominal swelling on the one hand, and train on the other. Not doing any of these things drastically reduces the chances of having a flat, toned stomach.

Let’s see for example what the coach Kayla Itsines , creator of the “Bikini Body” method to firm up the belly, suggests.
As you will see, these tips are also useful against bloating and reduction of abdominal fat.
HOW TO FIRM YOUR BELLY: KAYLA ITSINES ‘7 TIPS

1) Have a snack in the early afternoon: between lunch and dinner, it can often take up to six or seven hours. If you are not used to practices such as intermittent fasting, if you do not eat something after two hours from lunch, you risk finding yourself at dinner very hungry and the desire to eat whatever. Itsines recommends breaking the fast at the first sign of hunger, but with smart snacks that are protein-balanced and have a low glycemic impact. For example, 100 grams of Greek yogurt (about 60 calories) with a little stevia and cinnamon, on a light wholemeal wasa slice, plus a teaspoon of sugar-free jam or a little bitter cocoa. A 100 calorie satiating hunger breaker.
2) Cut back on salt by opting for natural foods, and avoiding salty snacks, sauces and packaged condiments instead. 
3) Chew long and slow, taking smaller bites, to avoid taking in air while you eat.