The Truth about Food Fat Percentages

One Calorie is the heat required to raise the temperature of one gram of water by 1°C. In dietetics (food matters) a kilocalorie (kcal) is equal to 1,000 calories.

The kcal therefore, measures the energy value of food in terms of its heat output: 1 oz  (28 grams) of protein yields 120 kcals, 1 oz (28g) carbohydrate yields 110 kcal, and 1 oz (28g) fat yields 270 kcal.  So, 1g of protein equates to 4.2 kcals, 1g of carbohydrate equates to 3.9 kcals and 1g of fat is 9.6 kcals.

Now for the important bit if you are trying to lose weight whilst eating healthily.  Losing, gaining or maintaining weight is a simple matter of adjusting the quantity of fuel you put into your body against the fuel your body uses.  If you put in more fuel than you use, you will gain weight and conversely if you take in less fuel than you use, weight loss will result.  I’ll state the obvious here just in case it didn’t come to mind, you can burn more kcals by doing some exercise.  The traditional swim, run, walk, cycle etc. are excellent forms of exercise but you could also think about other not so obvious forms which aren’t usually labelled as exercise such as housework, dancing, gardening etc.  In addition, you should try to get the correct balance of the composition of your diet through carbohydrates, proteins and fats as they are all important elements which the body requires.  You should be consuming approximately 60% carbs, 30% protein and 10% fat.  However, it is clear from the above information on food calorie contents that if you can reduce the fat content of foods you eat, you will be more easily able to eat fewer calories. 

When you see a food item that states its fat content, it is almost certain to be as a percentage of the weight of the product.  However, as you can see from the above kcal values for food types, fat has over twice the calorific content of proteins and carbohydrates.  In other words, if you are trying to lose weight and therefore reduce your calorific input, you need to work out the percentages in real fuel terms.  To do this you simply take the weight (in grammes) of the fat in the item and multiply it by 9.5 (kcals per gram of fat) then divide that by the total kcals of the item.  This will give you the fat content as a percentage based on calories and not weight.  Try it, it’s a real eye opener!  You can do the same for carbs and protein but use a multiplication factor of 4 (4 kcals per 1 g).  In additon, another little trick the food manufacturers use is to lower the fat content by increasing the overall calorie content.  Why do they do this?  Because people buy based on the wrapper marketing.  If during development a product has a 5% fat content (by weight) the manufaturers can add sugar to reduce the fat content as a percentage, but of course at the same time they increase the calories in the product.  But they know people will buy the product because the wrapper states “only 3 % fat”.  Do the calculation next time you see this and you will find it is more likely to be nearer to 50% fat as a percentage of calories.  If you also find a similar product not purporting to be a diet product, it might well have less total calories than the low fat product.  By doing this calculation you won’t be sucked in to the trap of the marketeers!


4 responses to “The Truth about Food Fat Percentages

  1. Great post Nick. I found it because Noel Ryan mentioned he’d read it.

    I wonder how different the label requirements are in the US and UK… here in the US most food packages contain: grams and % of “recommended daily allowance based on a 2000 kcal diet” of all three Carb/Protien/Fat macro-nutrient groups; they also list total calories (kcal) and total Fat Calories.

    Since the Atkins and other low carb diets have become such a big craze over here they also breakout carbohydrates into Fiber and Sugars. And sometimes if they want to market something as “low carb” they will include a stat the call “Net Carbs” which is essentially total carbs in grams minus the dietary fiber in grams.

    Also since various kinds of fat are considered more or less healthy, they also include Total Fat grams, Saturated Fat grams, Trans Fat grams, and Cholesterol grams.

    Other required elements of US labels include mg of sodium, and % “rda” of Vitamin A, C, Calcium and Iron.

    It always cracks me up to see disclaimers like “Not a significant source of xyz” or when they list out the vitamin content as 0%.

  2. Hi Nick

    Thanks for the info on Kcals ect. I have to eat food that are high in iron, will this cause me to gain alot of weight also, I use to run 100 meters for Birchfield Harriers before having my daughter and while pregnant my tummy musels split, is there any way I can build them up.

    Do you have any ideas that would motive me to do more excersie and eat heathly, I HAVE NO WILL POWER !!! Please help


  3. I am female, nearly 80 years old. I’d like to lose about 3 stone (42 pounds), but I don’t have much energy for exercising. How much exercise should I be getting?

  4. Hi Joyce
    At 80 years of age the first thing to consider is your current state of health and fitness. The key here would be to ensure you are capable of even a small amount of exercise and a once over by a doctor to give you the go ahead, is a real must. This will also give you that all important “line in the sand” as to your current stats and allow you to monitor your progress and use that success to spur you on further.
    Clearly, the more overweight you are the harder any form of exercise will be and the quicker you will tire. Ask anyone to pick up and carry a large sack of potatoes up the stairs and even fit people will become fatigued quite quickly. If you are working towards losing 3 stone (42 pounds), I have to assume that you are at least 3 stone (42 pounds) overweight and that is a considerable weight to have to carry around permanently. This weight, along with your age and your probable lack of exercise, will certainly be major contributors to your lack of energy. Your nutrition is also key, eating the right foods will make a huge difference to energy levels.
    Losing weight is not just about starting exercise, in fact, you don’t need to increase your current levels of exercise to lose weight. If you manage your calorie intake in proportion to your calorie expenditure the same effect can be achieved. Taking up exercise however, will enable you to reduce your intake less but still achieve weight loss as you will of course be burning more calories.
    In addition, taking up exercise will give you more energy and create a generally better feeling of well-being. So, to your question, if you are not getting any or very little exercise you must start slowly and steadily. You should be working towards achieving 4 sessions per week of preferably over 40 minutes. This might not be at the intensity of a younger person but it has to be relative to your age, weight and general condition. Try to spread the sessions evenly across the week so you have time to recover between each session. Then exercise should be low impact and ideally not weight bearing such as running. It is also important to remember though that anything you do during the day that uses energy will burn calories. So, if you keep this at the forefront of your mind and don’t take the easy options of for example, using remote controls, or the car to pop to the shops but instead make the effort to do it the way which uses more energy, you will be burning calories that would otherwise not have been used. Also, cutting back on calorie intake is a must. You need not calorie count but instead try this one and see how you get on. Try to eat natural foods that are vibrant in colour. It is a rule of thumb but if you lay out a table of highly processed fast foods, such as instant meals or instant meal ingredients the table will have lots of pale orange coloured foods on it. Mainly these will be high in calories, high in preservatives and low in nutrients and goodness. Home made soups are ideal, use all fresh vegetables, boil them up for 40 minutes, add some vegetable stock and blend it down to a soup. Tasty, very low in calories and high in goodness! Exercise will help with weight loss but ultimately, unless an individual has some imbalance within their bodily make up, it’s a simple calories in versus calories out struggle. The out must outweigh the in otherwise your goal will not be achieved.

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