The Glycemic Index Won’t Help You Lose Weight

Late­ly, many nutri­tion gurus have been try­ing to tell me that eat­ing a diet with a low glycemic index is the secret to los­ing weight. But if that were true, then car­rots would be more fat­ten­ing than fudge is.

Unfor­tu­nate­ly, the glycemic index is being used to steer peo­ple away from the sort of food that can real­ly help them lose weight and con­trol their blood sug­ar: unre­fined starch­es and veg­eta­bles. If you sur­vey the world’s pop­u­la­tions, you’ll find that the peo­ple who are eat­ing diets based on unre­fined starch­es and veg­eta­bles have low risks of obe­si­ty, heart dis­ease, dia­betes, and breast cancer—even though the glycemic index of their diet is high. In con­trast, the peo­ple who are eat­ing the most fat and protein—both of which tend to decrease the glycemic index of a meal—are the ones who are get­ting fat and sick.

The glycemic index was orig­i­nal­ly devel­oped to fine-tune the sys­tem of car­bo­hy­drate exchanges that peo­ple with type 1 dia­betes use to cal­cu­late how much insulin they will need to inject after a meal [1]. The glycemic index mea­sures the effect that 50 grams of carbs from any giv­en food has on your blood sug­ar. For exam­ple, if you ate 50 grams of car­bo­hy­drate from beans, your blood sug­ar wouldn’t go as high as if you ate 50 grams of car­bo­hy­drate from pota­toes instead. In oth­er words, beans have a low­er glycemic index than pota­toes do.

Like pota­toes, car­rots have a high glycemic index. How­ev­er, you’d have to eat about 4 cups of shred­ded car­rot to get 50 grams of car­bo­hy­drate. Thus, if you ate just one car­rot, it would have only a small effect on your blood sug­ar. To cor­rect for this prob­lem, some peo­ple use the glycemic load, which is the glycemic index mul­ti­plied by the total amount of car­bo­hy­drate in the food.

The glycemic index and glycemic load are of sur­pris­ing­ly lit­tle val­ue to dieters. One rea­son is that the glycemic index of any giv­en food is so hard to pre­dict. For exam­ple, you could increase the glycemic index of a pota­to by mash­ing it. Then, you could decrease the glycemic index of the mashed pota­to by adding milk and but­ter. Fats and pro­teins tend to decrease the glycemic index of a food. Although adding but­ter to a food decreas­es the food’s glycemic index, the but­ter does not make the food less fat­ten­ing!

Even if you eat a meal that has a high glycemic load, that doesn’t mean that your blood sug­ar is going to go dan­ger­ous­ly high. It all depends on your insulin sen­si­tiv­i­ty. Peo­ple who habit­u­al­ly eat a low-fat, starchy diet tend to have much small­er blood sug­ar swings than peo­ple who eat a high-fat, low-carb diet. Sci­en­tists have known that fact since the 1930s! In fact, a diet based on high-glycemic-load veg­eta­bles and unre­fined starch­es can restore the body’s insulin sen­si­tiv­i­ty, thus cur­ing type 2 dia­betes, with­in a mat­ter of weeks.

Ref­er­ence List

  1. Jenk­ins DJ, Wolever TM, Tay­lor RH et al. Glycemic index of foods: a phys­i­o­log­i­cal basis for car­bo­hy­drate exchange. Am J Clin Nutr 1981;34:362–366.

Note: For more infor­ma­tion about the con­trol of weight and blood sug­ar, see my book Thin Dia­betes, Fat Dia­betes: Pre­vent Type 1, Cure Type 2.

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