When you walk into a supermarket these days, you are confronted with an array of products claiming to be low fat! But before you reach out and plant that big bag of 95% fat free chips in your shopping basket, think again! The 'only 5% fat' and similar advertising claims found on food products, although true, can be somewhat misleading. The figures quoted are normally based on the percentage of fat in terms of weight only. The problem with this is twofold:
Reason 1. Firstly, as a healthy minded consumer you should be more concerned with the percentage of fat in terms of energy (calories), rather than weight. This is because a food product may contain a high percentage of non-caloric mass, notably water. Chips are a good example of this as they are over 50% water. Therefore, the fat content of chips in terms of weight would appear to make them a wise choice, but for the full picture you should also establish if a food has a high water content.
Reason 2. Secondly, analysing the fat content of food in terms of weight only can be misleading due to the fact that gram for gram, fat has over twice as many calories as either carbohydrates or protein.
Caloric Value of Macro Nutrients (per gram):
Therefore, to test whether a food is low fat or not, you should first find out the content of fat, carbohydrate and protein, and calculate the total caloric value that each nutrient contributes to the overall food. To demonstrate this, below is an example of oven chips advertised as 'only 5% fat' but shows the difference between fat content expressed as both weight and calories.
Oven Chips (advertised as only 5% fat)
Nutritional information per 100g serving (typical values of product cooked in oven):
|Weight (g)||Weight (%)||Kcals||Kcals (%)|
This shows that the 'fat weight' of the oven chips to be 5.1%, but the percentage of 'fat calories' to be a much higher 27.5%.