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.Firstly, as a healthy minded consumer you should be more concerned with the percentage of fat in terms of energy(calories),not 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 would appear to make them a wise choice, but for the full picture you should also establish if a food has high water content.
The second reason why using fat content of food in terms of weight only can be misleading is due to the fact that gram for gram, fat has over twice as many calories as either carbohydrates or protein (see Figure 1)
Figure 1 CALORIC VALUE OF MACRO NUTRIENTS(PER GRAM)
CARBOHYDRATE = 4 Kcals
PROTEIN = 4 Kcals
FAT (LIPIDS) = 9Kcals
Therefore, to test whether a food is low fat or not, you should first find out the weight content of fat and the other macro nutrients carbohydrates and protein, and calculate the total caloric value that each nutrients contributes to the overall food. To demostrate this,below are two examples of popular branded food products advertised as ‘only 5% fat’ and ‘85% fat free’ that shows the difference between fat content expressed in terms of weight and calories.
Examples 1 McCain Oven Chips (advertised as only 5% fat)
Nutritional information per 100g serving(typical values of product cooked in oven)
CARBOHYDRATE 27.7 weight (grams),27.5 % of total weight ,110.0 Energy (Kcals) 65.8% of total Kcals
PROTEIN 2.8 weight (grams), 2.8 % of total weight ,11.2 Energy (Kcals),6.7% of total Kcals
Fat 5.1 weight (grams), 5.1 % of total weight,45.9 Energy (Kcals),27.5% of total Kcals
Total 35.4 weight (grams), 35.4 % of total weight,167.1 Energy (Kcals),100.0% of total Kcals
Example 2. McVities Go Ahead! Carmel Crisp (advertised as 85% fat free)
Nutritional information per100g serving
CARBOHYDRATE:74.5 weight (grams) , 74.5 % of total weight , 298.0 Energy (Kcals),66.8% of total Kcals
Protein:45.0 weight (grams) , 4.4 % of total weight , 18.0 Energy (Kcals),4.0% of total Kcals
- Fat:14.5 weight (grams),14.5 % of total weight,130.5 Energy (Kcals),29.2% of total Kcals
Total:93.5 weight (grams),93.5 % of total weight,446.5 Energy (Kcals),100.0% of total Kcals
Example 1. shows the percentage fat weight of McCains Oven Chips to be 5.1 %, but the percentage calories to be a much higher 27.5%. Example2. shows a similar scenario with a product from the McVities GO Ahead range, where the fat content is a mere 14.5% by weight,but 29.2% in calorie.
hope i’ve this is of use, and your not asleep.