Resistant Starch, Weight and Body Fat

weight iconA lot of people are looking for help with controlling their weight. With focus and determination, people can lose weight, but they have a much harder time in maintaining the lower weight. Either they did not learn to eat healthy foods or they got tired of their diet plan and slid back into older eating habits. In any case, weight control is an overwhelming issue for many people.

Resistant starch does not make you lose weight by itself. But, it makes it easier for you to lose weight if you decide to. When researchers fed resistant starch to people as part of insulin sensitivity studies, they did not spontaneously lose weight. (see see Robertson 2005, and Johnston 2010). But, that’s not the end of the story.

Participants in the Robertson 2005 study experienced a small but significant increase in lean body mass. Additional studies have also demonstrated that resistant starch changes body composition and reduces fat storage. Some research, but not all, suggests that it increases satiety and reduces food consumption.

Researchers around the world are now focusing on the gut microbiome as a key mechanism for many aspects of metabolism. Animal studies have shown that resistant starch’s fermentation changes the expression of hundreds of genes within the large intestine. Some of these genes are known to be involved in key metabolic processes (including up-regulating GLP-1 and PYY), but their full impact and metabolic pathways are poorly understood. I won’t go into the microbiome pathways and processes, as research is still early and there’s a lot that we do not know. The important point I want to make is that fermentation is believed to be a critical and key mechanism for resistant starch’s impact on body fat and metabolism.

Here is how resistant starch can help with weight control and reducing body fat:

1. It reduces the energy content of foods. When it replaces flour or other high glycemic carbohydrates, the amount of glucose released into the small intestine goes down – the glycemic response is lower – directly lowering the four kilocalories/each gram of glucose released. Resistant starch is fermented in the large intestine, which produces short-chain fatty acids – another type of energy – estimated to contain between one and two kilocalories/gram to the human body.
One clinical study from the USDA found that men with higher than normal insulin levels derived 2.2 kilocalories/gram from high amylose resistant corn starch whereas men with normal insulin levels derived 2.8 kilocalories/gram. (Surprise – your metabolism impacts how much energy you derive from foods.)
– Animal studies confirm that resistant starch delivers between 2 and 3 kilocalories/gram.

2. Resistant starch’s fermentation lowers insulin levels. Insulin is a key metabolic hormone, which triggers cells to store fat. It also prevents fat from being burned as energy. Click here for more information on the metabolism of insulin sensitivity.

3. Resistant starch appears to impact satiety (feeling full after eating) and hunger. Five out of seven studies are supportive. It was surprising to find that people were less hungry 6-24 hours after the food was consumed, as one of the main mechanisms is large intestinal fermentation, which occurs many hours after eating.

a. Studies showing that resistant starch increases satiety:
van Amelsvoort AJCN 1992 (measured for 6 hours after eating),
Quilez JFS 2007 (measured for 2 hours after eating),
Nilsson JN 2008 (measured 10.5-12 hours after eating evening meal), and
Willis NR 2009 (measured for 3 hours after eating).

b. Studies which found no effect on satiety, but the participants ate significantly less food:
Bodinham BJN 2010 (at the next meal and over 24 hours)

c. Studies showing no effect on satiety:
Weststrate AJCN 1993 (measured for 6 hours after eating),
de Roos EJCN 1995 (measured over the entire day).

4. Resistant starch changes fat storage within adipose tissue and increases fat burning:

a. It increases lipid oxidation and reduces carbohydrate oxidation as measured by the Respiratory Quotient. (Tagliabue AJCN 1995, Higgins NM 2004)

b. It also reduces the abdominal adipose tissue release of non-esterified fatty acids (NEFAs) in healthy people (Robertson AJCN 2005, in individuals with Metabolic Syndrome (Robertson JCEM 2012) and in individuals with type 2 diabetes (Bodinham EC 2014). This suggests improved suppression of lipolysis (fat breakdown) with insulin.

c. Animal studies are consistently supportive – At least ten animal studies have shown reduced body fat after resistant starch consumption. Three animal studies have shown increased lean body mass. (See Higgins Critical Reviews in Food Science & Nutrition, 2014 for a summary or e-mail me for the details.)

Weight control is a tough goal. There are a lot of metabolic processes impacting weight, and it is difficult if not impossible to design clinical studies to measure the overlapping systems. The evidence suggests that resistant starch delivers less energy, can help people eat less food without being hungry and to reduce fat tissue. All of which are really important in weight control. Stay tuned – this is an active area under investigation.