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Skinny Without Willpower

Wednesday, April 28, 2010


Every now and then I hear people promoting low-fat diets, assuming that a low fat diet is naturally healthy. If fat in the body makes a person fat then it must be coming from the diet, right? It’s this simple logic that has spiraled much of the developed world into an epidemic of obesity in spite of the steady decline in overall fat consumption in our diets, thanks to the popular media and the high-carb advocates. But this couldn’t be farther from truth. The reason being that it is not the excess fat but the excess carbohydrates in our diets that gets converted to fat and stored in the adipose tissue. I have talked about the fat storage mechanism in my previous articles so I am not going to get into the details of it but I would like to reiterate that a healthy balanced diet must have ample quantities of mono-unsaturated fatty acids (MUFA) and omega-3 fatty acids.

Let’s look at why this low fat thinking won’t make people any slimmer. Take for example the raging success of low-fat yogurt parlors these days. I see these low-fat yogurt stores popping up all over the bay area faster than the weed in my lawn and people who have seen my lawn know what I am talking about. Their selling point is flavored low-fat yogurt and everyone seems to be raving about the low-fat aspect of it. So I went online to check the nutritional content of one such store and their offerings. Here is what it reads:

Figure 1.

So a small cup has two servings of these. There is no fat of course but looking at the sugar content it seems like a small cup would have about 4 teaspoons of sugar. And if you were someone like me and went for the large cup of the healthy stuff then you would end up getting about 52 grams or about 10 teaspoons of sugar. Now if you have been paying any attention to my previous articles you would know what eating sugar is going to do to your blood glucose levels and that getting fat has little to do with how much fat you eat but a lot more to do with your insulin response to sugars and high GI carbs. In fact the addition of a little healthy fat to this yogurt would be more wholesome and less fattening because fat slows the glucose response of carbs as illustrated in a study conducted in reference [1]. In this study ten healthy men received a 50-g portion of glucose alone and the same quantity mixed with butter, sunola oil (MUFA) or sunflower oil (PUFA) on separate days. Blood was collected at regular intervals for 2 h. The glycemic index (GI), insulin index (II) were calculated from the blood-work. It was found that addition of fat to a carb meal blunts the rise in blood glucose levels (shown in figure 2) following the meal which means smaller insulin response and less fat storage (remember, insulin is basically a storage hormone).

Figure 2.

So, from the way I see it, adding some healthy fat especially to a high GI carb meal would have the following benefits:

1) As illustrated above, fat slows the glucose spike in your blood from high GI carbs like sugar and starches.

2) Fat triggers the satiety centers in your brain and fills you up so you end up feeling fuller quicker (and you thought it was the guilt of eating fat that made you stop eating sooner).

3) Fat also slows your digestion and keeps your fuller longer so you don’t go for the next carb meal as quickly.

So the next time you go for a low-fat meal read the label closely for the amount of sugar or carb in a serving and even if it’s the most healthiest thing in the world adding some healthy fat from almond butter or such will only make it healthier.

Joannic, J.-L., Auboiron, S., Raison, J., Basdevant, A., Bornet, F. & Guy-Grand, B. (1997) How the degree of unsaturation of dietary fatty acids influences the glucose and insulin responses to different carbohydrates in mixed meals. Am. J. Clin. Nutr. 65:1427-1433.


  1. great post. I always see the previous generation (my dad/uncles) and they consume quite a lot of fat than I do - but don't have any problems. I think if we focus on the right food and right activity, anything is OK (in right amounts)!