How Does This Salivary Enzyme Affect Weight Gain? (AMY1A)

Amylase is an enzyme that breaks down starch into simpler sugars. Digestion of carbs is extremely important since carbs are ultimately broken down into glucose, the main energy source that fuels our bodies.

There are two main types of amylase: salivary and pancreatic. Salivary amylase is produced by salivary glands and it starts digesting food as you chew it. Pancreatic amylase is produced by the pancreas and helps digest complex sugars in your gut [R, R, R].

Humans have two primary amylase genes: AMY1A and AMY2A. The first, AMY1A, encodes salivary amylase (alpha-amylase 1A), while AMY2A encodes pancreatic alpha-amylase (alpha-amylase 2A). In this post, we will be focusing on the first type: salivary amylase (AMY1A) [R, R].

Amylase breaks down complex carbs like starch into simple sugars. There are two broad types: salivary amylase (encoded by the AMY1A gene) and pancreatic amylase (AMY2A).

Lower expression of AMY1A has been associated with a higher body mass index (BMI) and obesity. This was shown in multiple studies with over 7,500 people. For example, one study suggests a person with less than 4 copies might have an eight-fold higher risk of obesity compared to a person with over 9 copies [R, R, R, R]!

Genetic variations (SNP) in AMY1 (rs11185098) that predispose people to higher amylase were associated with weight loss. When put on a diet, people with the higher amylase ‘A’ variant tended to lose more weight than people without the ‘A’ variant. The study included over 800 obese participants monitored for 2 years [R].

Higher amylase activity is also linked to better glucose tolerance after eating starch. It was associated with a decreased risk of insulin resistance, metabolic syndrome, and type 2 diabetes, according to studies of over 3,500 people [R, R].

Low expression of amylase (fewer copies) has been associated with glucose malabsorption and lower ability to digest and use complex carbs [R].

Low amylase and obesity can also affect each other in a vicious cycle. On one hand, studies have found that having low amylase levels is associated with an increased risk of obesity [R, R, R, R].

On the other hand, being obese lowers amylase levels, possibly by affecting insulin production and sensitivity. One way to put an end to this harmful loop is weight loss, which increased amylase levels in a subset of 4 obese people monitored over a year [R].

In multiple studies, genetic variants that reduce amylase expression have been associated with poor sugar metabolism, obesity, and weight gain.

Amylase & Your Gut Flora

Scientists have found a link between AMY1A copies and gut bacteria. People with more copies may have more bacteria that can ferment resistant starch and more beneficial short-chain fatty acids such as butyrate in the gut [R, R].

There is some controversy over whether increased butyrate production in the colon is protective against obesity. However, most available research has found that a higher share of butyrate (compared to other short chain fatty acids) appears to protect against diet-induced weight gain. Supplemental butyrate may even speed up metabolism and increase energy expenditure [R, R].

One way amylase may affect weight is through the gut flora; people with higher amylase expression may have more gut bacteria that ferment resistant starch into butyrate.

At least four AMY1A variants have been associated with weight gain in humans. In each case, the detrimental allele is associated with reduced amylase activity, possibly due to a reduced number of amylase copies produced [R, R].

The variants associated with lower amylase activity and an increased potential for weight gain include rs11185098-G, rs4244372-A, rs11577390-C, and rs1999478 [R, R].

SNP Summary and Table

AMY1A rs11185098

• ‘G’ = Associated with decreased amylase activity and a tendency to regain weight that was previously lost
• ‘A’ = Associated with increased amylase activity and a tendency to keep weight off once lost

AMY1A rs4244372

• ‘T’ = Associated with increased amylase activity and relatively reduced weight gain
• ‘A’ = Associated with decreased amylase activity and relatively increased weight gain in women

AMY1A rs11577390

• ‘C’ = Associated with decreased amylase activity and relatively increased weight gain in women
• ‘T’ = Associated with increased amylase activity and relatively reduced weight gain

AMY1A rs1999478

• ‘C’ = Associated with increased amylase activity and relatively reduced weight gain
• ‘A’ = Associated with decreased amylase activity and relatively increased weight gain in women