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Calories, Portion and Serving Sizes

Decorated Gourmet Meal

Posted: 23/02/2018

Updated: 06/05/2018

Did you know that a third of the people in the UK underestimate how much they eat typically by 1000 calories? Research attributed obesity to portion sizes, meals eaten outside, ready meals and junk food.


Portion sizes are important when it comes to weight loss. You may be eating healthily but still, be packing on the pounds as portions sizes are often out of control these days especially when you’re eating out. A few extra spoonsful every day can easily result in weight gain over time. 


In this article, portion and serving sizes will be discussed but first, we need to address how much food our body actually needs. 


How much do we need?

The average energy recommendation to maintain weight for men and women is 2500 and 2000 calories per day, respectively. But what does this mean?


A calorie is a unit of energy that our body needs to function which includes basic metabolic processes and the activity you engage in throughout the day. In nutrition sense, it includes all foods - carbohydrates, fats, proteins. 


Calorie needs are different for everyone, depending on your age, sex, height, weight, activity level and goals.


For adult women, estimates range from 1600 to 2400 calories per day and 2000 to 3000 calories per day for men.


To find out what your daily caloric needs are, you can use calorie calculators online that are based on different formulas or calculate them yourself. The two most commonly used formulas are shown below. 

Calorie counting


655.1 + (9.6 x Weight in kg) + (1.9 x Height in cm) – (4.7 x age)


66.5 + (13.8 x Weight in kg) + (5 x Height in cm) – (6.8 x age)


The results known as your basal metabolic rate (BMR) are then multiplied by the activity factor which is dependent on a person's typical levels of exercise.


​​BMR x Activity factor = calories per day to maintain weight


10 x (Weight in kg) + 6.25 x (Height in cm) - 5 x age - 161


10 x (Weight in kg) + 6.25 x (Height in cm) - 5 x age + 5

Again, these results are multiplied by the activity factor.​​

Mifflin-St. Jeor Equation (more accurate)

Note: as these equations do not take into account of body composition, they are highly inaccurate for both muscular and obese individuals. If they have the same sex, weight, height and age, it will result in the same BMR values.

Calorie Counting

Now that you’ve estimated your daily total energy requirements, you can calorie count, right?


By eating fewer calories than you burn, you can lose weight, right? Yes, in theory, and it sounds simple. 


But actually managing your food intake based on calorie counting is extremely difficult.


Even if you do measure the ingredients that you use, cooking can alter their nutritional profile and the number of calories present in the same quantity. To make it tougher, the databases are often inaccurate and hence you could be under or overestimating the calories on your plate.


In addition to this, you may be keeping track of the quantity of what you put in your body but not the quality of your diet. The quality of the overall diet based on the types of food you eat can impact your health, body composition, mental wellbeing, energy levels and so much more.


A nutritionally unsound low-calorie diet is doomed to fail as it will increase food cravingshunger signals and make you more prone to binge eating.


To put it simply, 100 calories of sweets will affect your health differently than 100 calories of broccoli.

KitKat (2 Finger Bar) Weight: 21g

Calories: 107

Broccoli (1/2 bunch)

Weight: ~350g

Calories: ~100 

Calorie counting may not suit everyone but if done properly - that is having a reliable database and meeting nutrient needs - it can result in healthy weight loss.


For others, a more flexible approach can be taken to plan your meals - by learning your serving and portion sizes.  

Serving portion size

Serving and portion sizes

Although these two terms are used interchangeably, serving sizes are actually different from portion sizes.


An unmeasured amount of food that you choose for your meal like a plateful of pasta.

estimate serving


A standardised amount of food or drinks that professionals recommend you eat in one sitting.

1 large tomato

1 small apple

2 medium whole carrots

3 large strawberries

1 medium banana

1 medium potato

The recommended serving size is typically less than the portion you are served.

Serving sizes can be typically found on the nutrition fact label behind food products.

1 can of crisps can contain 12 servings


This can be a bit misleading as the entire can of crisps actually contain 1320 calories and quite often we finish the entire can in one sitting.


You may realise how little one serving can be compared to what you usually consume. This is due to the fact that all products nowadays are "supersized".


Understanding serving sizes is a good starting point to guide us to eat appropriate amounts of food and avoid overconsumption.

putting into practice

Now the question arises so what is one serving in each food group?

How to estimate a serving

Instead of carrying scales and weighing the food that we eat, we can make sense of serving sizes by using our hands. The best part is they are personalised and portable making it the best device for measuring food intake.

rice, pasta

fruit, vegetables

milk, yoghurt


Two fists







nuts, raisins


Thumb tip

peanut butter

hard cheese

cooking oil




A different approach is:


fruits, vegetables







Putting it into practice

The DASH Diet (Dietary Approaches to Stop Hypertension) is the go-to diet plan for lowering blood pressure in most doctors and dietitians.


The DASH diet was ranked the best by the U.S News & World Report for the sixth year in a row in 2016 and hence, I will be using this as an example to show how serving sizes can be put into practice.


Here, servings are used in each food category to help determine how much you should eat to meet the plan’s daily recommendation.

Food Type


For a 1600 calorie diet per day


3 - 4


2 - 3

3 - 6 oz


3 - 4





Fat-free or low-fat dairy products

Lean meats, poultry and seafood

Fats and oils

Nuts, seeds, and legumes

Sweets and added sugars

For a 2000 calorie diet per day

6 - 8

4 - 5​

4 - 5

2 - 3

< 6 oz

2 - 3

4 - 5

< 5

Data from the American Heart Association


As you can see, how many servings you need really depends on how many calories you need for your body to function


Serving sizes are extremely flexible and you can always adjust your portions based on your hunger, satiety and goals.

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