To maintain a healthy weight, the amount of food you eat is just as crucial as what you eat. The amount of food you choose to eat at one time is called a portion, while the amount listed on a food label is called a serving. The amount of food you should eat may not always match the serving size on a food label. This is because the number of calories you need each day to maintain or lose weight can vary depending on factors such as your age, current weight and height, metabolism, gender, and activity level. For instance, a woman who only takes short walks once a week will require fewer calories compared to a woman of similar size who engages in intense physical activity like running multiple times a week.

Portion sizes
Fill half your plate with vegetables and fruits for a healthy meal. Remember, potatoes are not considered vegetables due to their impact on blood sugar levels.
Include whole grains on a quarter of your plate. Whole grains such as whole wheat, barley, quinoa, and brown rice have a better effect on blood sugar compared to refined grains, including white bread and white rice.
Add protein to a quarter of your plate with options such as tofu, beans, and nuts. Limit red meat and avoid processed meats, including bacon and sausage, for a healthier choice.
Use healthy plant oils in moderation. Opt for healthy vegetable oils such as olive, canola, soy, corn, sunflower, peanut, and others. Avoid partially hydrogenated oils that have unhealthy trans fats. Keep in mind that low-fat doesn’t necessarily mean “healthy.”
Make wise choices with your beverages. Stay hydrated by drinking water, coffee, or tea. Avoid sugary drinks, and limit your intake of milk and dairy products to one to two servings per day. Additionally, restrict your juice consumption to a small glass per day, as they are high in calories and offer little nutritional value.

Mainly, focus on the quality of your diet. For example, the type of carbohydrate you consume is more important than the quantity. Certain sources of carbohydrates, including vegetables (excluding potatoes), fruits, whole grains, and beans, are considered healthier options.

How to control food portions at home
You do not have to constantly measure and count everything you consume. It is advisable to do so initially to understand standard serving sizes. Implement the following strategies to manage portions at home:
Consume your food from a plate rather than directly from the packaging.
Avoid eating while watching TV, driving, walking, or engaging in other activities.
Eat slowly to allow your brain to register when your stomach is full, which typically takes around 15 minutes. If you prepare excess food, freeze the leftovers for later consumption. This prevents you from being tempted to finish the entire batch.
Limit the consumption of high-fat, high-calorie foods, including desserts, chips, sauces, and packaged snacks.
Maintain a regular meal schedule to avoid overeating later in the day due to delayed or skipped meals.

How to control food portions when eating out
Managing portions when eating out can be challenging. While it’s easier to control portions when cooking at home, there are still ways to manage your food intake when dining out. Implement the following strategies to manage portions when eating out:
Avoid all-you-can-eat buffets and opt for restaurants that offer healthier food choices in controlled portions.
Instead of ordering a full meal, consider selecting one or two healthy appetizers or side dishes.
Request to have the basket of bread or chips removed from the table to avoid mindless snacking.
If possible, choose smaller portions instead of their larger counterparts.
Listen to your body’s signals, and stop eating when you feel full. Put down your fork and glass, and focus on enjoying the company and ambiance of the restaurant. Remember, practicing portion control when eating out can help you maintain a balanced diet and make healthier choices.

Sources:
https://www.niddk.nih.gov/health-information/weight-management/just-enough-food-portions#:~:text=A%20portion%20is%20how%20much,products%20have%20different%20serving%20sizes.
https://www.hsph.harvard.edu/nutritionsource/healthy-eating-plate/