Sunday, February 1, 2015

Starch is not more fattening than sugar

Background


Ray Peat repeatedly claims that starch is more fattening than sugar. He bases this argument on differences in insulin/glucose dynamics and animal feeding studies.

Eating “complex carbohydrates,” rather than sugars, is a reasonable way to promote obesity. Eating starch, by increasing insulin and lowering the blood sugar, stimulates the appetite, causing a person to eat more, so the effect on fat production becomes much larger than when equal amounts of sugar and starch are eaten.” -Ray Peat in "Glycemia, starch, and sugar in context"
"Fructose inhibits the stimulation of insulin by glucose, so this means that eating ordinary sugar, sucrose (a disaccharide, consisting of glucose and fructose), in place of starch, will reduce the tendency to store fat." -Ray Peat in "Glycemia, starch, and sugar in context"
“Starch is less harmful when eaten with saturated fat, but it’s still more fattening than sugars.” -Ray Peat (Quote found on FPS)
“When starch is well cooked, and eaten with some fat and the essential nutrients, it’s safe, except that it’s more likely than sugar to produce fat, and isn’t as effective for mineral balance.” -Ray Peat (E-Mail advice)
Paradoxically, the vast majority of people who switch from a high-starch diet to a low-starch high-sucrose peatarian diet gain weight. What does the experimental human evidence say?

Relevant studies


  • In a 14-day crossover study, 20 normal-weight healthy women ate a diet at their own pleasure (ad libitium), that was either rich in fat, starch or sucrose while keeping protein intake stable. After 14 days, the women lost weight on the starch diet (mean -0.7kg), while weight on the sucrose diet remained stable (mean +0.2kg). The difference in weight was likely mediated by differences in caloric intake, with women on the ad libitum high-sugar diet eating a higher amount of calories compared to the starch diet. http://www.ncbi.nlm.nih.gov/pubmed/9347402
  • In a 6 week randomized crossover trial, 13 healthy males consumed either a higher-starch or a higher-sucrose diet while keeping total carbohydrates and energy intake stable. After 6 weeks, there was no significant difference in weight. Total and LDL cholesterol was higher in the higher-sucrose diet compared to the starch diet. Fasting glucose was unchanged but fasting insulin tended to be higher in the sucrose diet. http://www.ncbi.nlm.nih.gov/pubmed/17130505
  • In a well designed 6-month randomized trial, 398 obese men and women ate ad libitum either a low-fat high-simple carbohydrate, a low-fat high complex-carbohydrate or a control diet. After 6 months, people in both low-fat diets lost weight compared to the control diet. The starch diet tended to be slightly superior (mean -1.8kg) than the sugar diet (mean -0.9kg) but the result was not significant and people seemed to eat more on the sugar diet. There was also a trend of an increase in insulin levels on the sucrose diet, while on the starch diet there was a trend of decreased levels compared to baseline. Fasting glucose tended to decrease more on the starch than on the sugar diet. http://www.ncbi.nlm.nih.gov/pubmed/11093293
  • A meta-analysis of trials that tested isoenergetic exchanges of free sugars with other carbohydrates found no significant difference in body weight (a minimal trend of higher weight was seen in the higher sugar groups). http://www.ncbi.nlm.nih.gov/pubmed/23321486

Conclusions 

Ray Peats view of starch as being inherently more fattening than sugar is not in line with the experimental human evidence or the reports by peatarians. If you like trends then starch even seems to beat sugar in terms of weight loss. But if you really look objectively, then the only conclusion is that there is no difference whether you consume starches or sugar and the main determinant of body weight is total caloric intake. Peat's reasoning on starch's effects on insulin and hunger is also not in line with the human evidence: Starch was neither more insulinogenic nor did it lead to higher food-intake. The studies even suggest the opposite, that sugar is slightly more insulinogenic and leads to higher subsequent food intake than starches. 

There are 3 important points that are rarely mentioned by Ray Peat but play a big role when comparing starches and sugar:

  1. Palatability and reward: There is good evidence that both palatability and reward are big determinants of total caloric intake. Easy palatable and rewarding foods, such as refined or sugared starch or non-starch products (i.e. cake, ice cream) increase overall caloric intake, contributing to weight gain, while shifting your diet to less palatable and rewarding food will promote weight loss. For more details I recommend the insightful review by Stephan Guyenet (1, 2).
  2. Liquid vs. solid foods: Likewise, there is good data that liquid foods are less satiating and suppress subsequent caloric intake less than solid foods (3). This is especially true for sugar-sweetened beverages which have been repeatedly in both observational and interventional studies shown to lead to weight gain and promote obesity (4). One explanation is that due to the rapid absorption of liquids in the gut, they cause less gastric stretch. Gastric stretch is an important trigger of satiety by activating stretch receptors (5).
  3. Type of starch: When people report they gain weight on starches, they should critically analyze their overall calorie intake and the type of starches they consume. Starches are often eaten together with fat or sugar (i.e. in cakes, cookies, pizza etc.) which make it easier to consume a larger amount of calories for the same satiety signal. This also makes comparison with fruits, with their inherently lower calorie content unfair, which are often not sufficient to satiate people alone. Sticking with more basic starches and combining them with less fat can already make a big difference.
At last, individual differences should not be discarded. It could be that some people are just born to be efficient starch-eaters while others run better on sugar-rich foods. For instance, the gene copy number of salivary amylase (which cuts down starch into sugar in the mouth) varies widely between people and could determine starch digestibility (6). People with a low copy number of salivary amylase were found to have a higher BMI, suggesting that efficient starch digestion leads to a quicker satiety feeling and thereby less overconsumption (7).  Differences in gut microbiome composition is another factor possibly involved in starch tolerability (8).

4 comments:

  1. Anonymous29/5/15 23:01

    If you gave people a diet of grass and a diet of sugar, they would probably lose more weight on the grass diet as well. This does not mean grass is an ideal source of calories.

    Starch, by virtue of being rapidly absorbed and made entirely of glucose, causes a bigger spike in insulin. This lowers the blood sugar, increases hunger, and raises the stress hormones.

    Sucrose, which is comprised of fructose and glucose, provides a more stable source of carbohydrate calories, as fructose does not generate nearly as great an insulin response as pure glucose, and is know to increase cellular metabolism to a greater extent than glucose.

    Peat's assertion that starch promotes obesity is perfectly reasonable when you consider the insulin-spiking effect of glucose, the rapid drop in blood sugar and consequent increase in hunger that accompanies it.

    I don't think starch is evil, and neither does Peat. But as he says, if there are better carbohydrate sources available, sources that balance blood sugar rather than disrupting it [fruit], why not choose those instead?

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    1. You are repeating just the same argument that I critically discussed in the blog article above without providing any additional proof for your hypothesis (starch-insulin-hunger-weight gain hypothesis). The studies above show that there is no difference in weight and that sucrose can increase stress hormones more than starch (see first reference).

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  2. In the studies above, the common metric is weight. Losing weight isn't necessarily healthy. In fact I think many people find they weigh more when they lose fat tissue and grow muscle tissue(healthy). I suspect the subjects in the above studies could have lost weight AND gained fat. I would like to see the effect of starch vs sucrose on Fat Percentage.

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  3. Wouldnt higher insulin mean less cortisol?

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