No matter the time of year, it seems as though swimsuit season is always just around the corner, which means it's always time to be thinking about how to eat better for a flatter belly. Eating specific foods can't help you spot-reduce. But the best foods to help jump-start your weight loss and flatten your belly are those that are low in calories and high in nutrients. Consult a health care practitioner before starting any weight-loss diet.

High-Fiber Fruits and Vegetables

A 2015 study published in the Annals of Internal Medicine found that adding fiber to your diet is an effective and easy change that can help you lose weight. Fruits and vegetables are naturally good sources of fiber.

But to really up your intake, consider adding raspberries, which have 8 grams of fiber per cup; cooked brussels sprouts, which have 6 grams of fiber per cup; and cooked collards, with 5 grams per cup.

Based on the Institute of Medicine fiber recommendations, women should try to eat 21 to 25 grams of fiber a day, while men should get 30 to 38 grams of fiber a day.

The Right Grains

Harvard Health Publications says that if you're trying to lose belly fat, you should limit your intake of refined carbs and replace them with more whole grains.

Quinoa is an excellent source of fiber and one of the best grain sources of protein.

Another good grain option to help jump-start your weight loss for a flatter belly is barley. A 2012 review article published in the Journal of Nutrition and Metabolism reports that barley is a highly satiating food and may help you stick to your reduced-calorie weight-loss diet.

Keep It Lean With Protein

When it comes to hunger control, protein foods beat out fiber, according to the European Food Information Council.

Salmon is not only a good source of protein, with 17 grams in a 3-ounce portion, but it's also rich in omega-3 fatty acids, which may also help promote meal satiety and weight loss.

Plain nonfat Greek yogurt contains 17 grams of protein per 6-ounce container and is rich in calcium.

And to get both protein and fiber, add lentils to your belly-busting diet. They have 17 grams of protein and 16 grams of fiber per cooked cup.

Better Fat, Better Belly

You may avoid fat in your diet for fear that it may hasten your weight loss, but Harvard Health Publications suggests replacing unhealthy saturated fat with healthy polyunsaturated fats to help decrease belly fat.

Instead of butter, use soy oil in cooking.

Walnuts are rich in polyunsaturated fats and make a healthy snack option on your diet plan.