Are Potatoes Fattening?

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According to a recent Harvard study, the daily consumption of each serv- ing of boiled or baked potato lead to the gain of 0.57 lb over the next 4 years. Not nearly as bad as French fries and potato chips but their results found each serving of boiled or baked potatoes was more likely to lead to weight gain than adding

a serving of butter, cheese, refined grains, or even an extra serving daily of sweets and desserts! Of course nearly all the baked and boiled potatoes consumed are loaded high fat items but they tried to control for that. Could the butter one adds to a boiled or baked potato be less fat- tening than the potato itself? Yes, if you believe what the authors told the media. The study itself did not ex- plain why potatoes were particularly fattening but in media reports we see quotes like this from the authors: “Although the study did not evaluate why potatoes would be particularly fattening, other research shows that starches and refined carbohydrates such as potatoes cause blood sugar and insulin to surge, which makes people feel less satisfied and eat

more as a result”, Dr. Mozaffar- ian said. [Rob Stein in Washington Post 6/23/11]. Such speculation puts these Harvard researchers in the same pseudoscientific camp as Atkins, Sears (Zone Diet), Agatston (South Beach Diet), and numerous other fad diet book authors.

Research has shown that both increased blood glucose and insulin reduce hunger. In the brain insu- lin acts as a satiety hormone and reduces hunger. A study done in Australia that examined that meas- ured satiety both objectively and subjectively after consuming 240 kcal from 38 different food items found that a plain boiled potato was the single most satiating food tested. The potato was far more satiating than peanuts, apples, fish, yogurt, cheese, or oatmeal.1 Back in the 1970s the Japanese consumed what was arguably the highest glycemic load diet in human history with only about 15% of their calories coming from fat and the bulk of their calories coming from the very high GI short grain rice and yet overweight and obesity were rare there.

One of the best predictors of both short-term and long-term hunger/ satiety is the stomach-produced hor- mone called ghrelin. People with the Prader-Willi Syndrome have insatia- ble appetites and have ghrelin levels 4-5 times normal. Ghrelin is called the “hunger hormone” so anything that reduces it should reduce food intake in the short and long term. Re- search shows that the ingestion of a starch-rich meal is better at reducing ghrelin and hunger than an isocaloric high-fat meal.2

Bottom Line: Dr. Mozzafarin’s study not withstanding it would be pre- mature at best to focus on glycemic load to enhance long-term weight control. It seems patently absurd to postulate that dietary advice to re- duce the intake of boiled and baked potatoes served with fat-free sour cream, salsa or mustard to lead to weight loss to prevent weight gain or aid weight loss.

By James J Kenney, PHD, RD, FACN.

1. Euro J Clin Nutr 1995;49:675-90 2. J Clin Endo Metab 2003;88:1577-86

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