What the research tells us about beta-glucan, appetite, weight and metabolic health.

Oats (Avena sativa) have been part of human diets for thousands of years. Evidence suggests that people cultivated oats as far back as 2000 BC. (Alemayehu et al. 2023).

But what makes oats different from other cereal grains?

Compared with many other cereals, oats contain relatively high amounts of protein and fat, with a greater proportion of this fat being unsaturated. Avenanthramides (AVAs) occur in oats, forming a polyphenolic group studied for antioxidant activity and health benefits (Alemayehu et al. 2023).

Perhaps one of the most well-known components of oats, however, is beta-glucan. Beta-glucan is a type of soluble fibre found mainly in the cell walls of the oat endosperm and in the bran of whole-grain oats.

So, does eating oats actually translate into better health?

The evidence is promising. A review of the research found that eating oats was associated with lower body weight, smaller waist measurements and less body fat (Matthews et al. 2023). However, these findings need to be interpreted carefully, as the research included different types of studies, which don’t all provide the same level of evidence.

So far, the science sounds promising—but what happens when people actually eat oats?

When people include oats in their diet, several studies report reductions in body weight and BMI. Some have also reported reductions in body fat, waist measurements and improvements in cholesterol and blood glucose.

But the studies have used oats in different ways. In some, oats were added to the usual diet. In others, they replaced staple foods or were incorporated into a broader dietary programme.

Let’s take a closer look.

Adding oats to the diet

One study from Brazil asked participants to add 40 g of oat porridge to their usual diet every day for eight weeks, preferably at breakfast. The control group made no dietary changes (Schuster et al. 2015).

Interestingly, the oat group experienced a significant reduction in body weight and BMI, alongside improvements in lipid profile, blood glucose and insulin resistance.

What’s particularly interesting here is that the participants weren’t simply told to replace another food with oats or follow a calorie-restricted diet. They were asked to add oats to their usual diet (Schuster et al. 2015).

What if oats replace other foods?

Another study looked at people with a BMI of 27 or above who consumed a beta-glucan-containing oat cereal twice a day for 12 weeks. The oat cereal replaced some of their usual staple foods (Chang et al. 2013).

After 12 weeks, the oat group had reductions in body weight and BMI. More than 60% of the participants also experienced reductions in body fat and waist-to-hip ratio (Chang et al. 2013).

There were benefits beyond body composition too. Total cholesterol and LDL cholesterol decreased, while some markers of liver function also improved (Chang et al. 2013).

This study is interesting because the oats weren’t simply added on top of the participants’ existing diet—they replaced some of their usual staple foods.

So, alongside the Brazilian study where oats were added to the usual diet, we now have two different dietary situations in which oat consumption was associated with reductions in body weight and improvements in metabolic health.

And then there’s the longer-term evidence

One particularly interesting study involved 298 people with overweight and type 2 diabetes.

For the first 30 days, participants lived in a hotel and ate their meals together, allowing their diets to be more closely controlled. Two of the groups consumed oats as part of a low-fat, high-fibre diet—one group received 50 g of oats per day, while the other received 100 g (Li et al. 2016).

After 30 days, participants returned home and were asked to continue following their assigned diet for another year (Li et al. 2016).

Both the short- and long-term results were encouraging. Compared with the non-oats diet, the oat groups experienced improvements in several important markers of metabolic health(Li et al. 2016).

For example, their post-meal blood glucose levels were lower. This is known as postprandial glucose (PPG)—essentially, how high your blood sugar rises after eating. They also had improvements in HOMA-IR, a measure used to estimate insulin resistance. In simple terms, better insulin sensitivity means the body can respond more effectively to insulin and regulate blood glucose (Li et al. 2016).

The oat groups also had lower total cholesterol and LDL cholesterol. LDL is often referred to as “bad” cholesterol because higher levels are associated with a greater risk of cardiovascular disease (Li et al. 2016).

And importantly, the participants also experienced reductions in body weight.

So the benefits weren’t limited to the number on the scales. The oat groups also showed improvements in several measures linked to blood glucose regulation and cardiovascular health (Li et al. 2016).

But the most interesting part was what happened next.

The improvements were maintained after one year.

And the group consuming 100 g of oats per day experienced significantly greater weight loss than the other groups (Li et al.  2016).

So What is it about oats that could produce these effects?

One possible explanation is beta-glucan.

Beta-glucan can increase the viscosity of the contents of the intestine, which may slow the digestion and absorption of carbohydrates and lipids. This can help reduce the rise in blood glucose after eating (Li et al. 2016).

Beta-glucan is also fermented by the gut microbiota, producing short-chain fatty acids (SCFAs) that may have a range of effects on metabolic health.

And beta-glucan may do more than influence blood glucose.

Research suggests that it can also affect satiety, gastric emptying and gut hormones, including PYY and ghrelin. PYY is involved in signalling fullness and reducing food intake, while ghrelin is involved in signalling hunger (Matthews et al. 2023).

What Happens If We Add Oat Bran to the Diet?

The potential benefits of oats aren’t limited to weight management.

In a study of pregnant women with gestational diabetes, participants following a standard diet for gestational diabetes were divided into two groups. One group also consumed 30 g of oat bran with lunch and dinner each day for four weeks.

The oat-bran group experienced reductions in both fasting blood glucose and two-hour postprandial glucose compared with the control group (Barati et al.  2021).

But what if you’re already in a calorie deficit?

This is where things get particularly interesting.

If oats really help with weight management, would adding them to a diet where calories are already restricted lead to more weight loss?

One 12-week study compared two groups following a 500 kcal daily calorie deficit. One group ate a low-fibre breakfast, while the other consumed 40 g of oats twice a day (Maki et al. 2010).

Both groups lost weight.

However, the oat group experienced a greater reduction in waist circumference, as well as greater reductions in total cholesterol, LDL cholesterol and non-HDL cholesterol (Maki et al. 2010).

Importantly, there was no significant difference in total weight loss between the two groups, nor were there significant differences in triglycerides or HDL cholesterol (Maki et al. 2010).

Key Takeaways

So, should you avoid oats if you want to lose weight? The research doesn’t suggest that you need to.

Here’s what the research suggests:

Oats may support weight management. Several studies have reported reductions in body weight, BMI, body fat or waist measurements when oats were included in the diet.

Beta-glucan may be an important part of the story. This soluble fibre can slow digestion, influence blood glucose, and may affect feelings of fullness and gut hormones.The benefits may go beyond weight. Studies have also found improvements in cholesterol, blood glucose and insulin sensitivity.

Oats are a nutritious source of fibre, including beta-glucan, and the research suggests they can be part of a healthy diet that supports weight management and metabolic health.

One final tip: choose your oats carefully

However, it’s worth paying attention to which oat product you choose. Avoid added sugars or glucose syrup found in some instant oat products by checking the ingredient list. Plain oats are a much simpler choice.

How do I like my oats?

Personally, I usually cook my oats with water or oat milk, then add a spoonful of nut butter — almond butter is my favourite.

I also like to add a handful of macadamia nuts and walnuts, along with a sliced banana.

It makes a delicious, filling breakfast and gives me a combination of fibre, healthy fats, carbohydrates and some protein to start the day.

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Visit my website to learn more about my nutritional therapy services, or book a free 15-minute discovery call to discuss your goals and see how I can support you.

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Want to make your breakfast more nutritious?

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References

Alemayehu, G.F. (2023). ‘Nutritional and Phytochemical Composition and Associated Health Benefits of Oat (Avena sativa) Grains and Oat-Based Fermented Food Products’, The scientific World Journal, pp. 1-16

Barati Z. et al. (2021). ‘The effect of oat bran consumption on gestational diabetes: a randomized controlled clinical trial’, (21)67

Chang, H.C. (2013). ‘Oat Prevents Obesity and Abdominal Fat Distribution, and Improves Liver Function in Humans’, Plant Foods Hum Nutr, (68) pp. 18–23

Li, X. et al. (2016). ‘Short- and Long-Term Effects of Wholegrain Oat Intake on Weight Management and Glucolipid Metabolism in Overweight Type-2 Diabetics: A Randomized Control Trial’, Nutrients (8)9, p. 549

Maki, K.C. et al. (2010). ‘Whole-Grain Ready-to-Eat Oat Cereal, as Part of a Dietary Program for Weight Loss, Reduces Low-Density Lipoprotein Cholesterol in Adults with Overweight and Obesity More than a Dietary Program Including Low-Fiber Control Foods’, Journal of the American Dietetic Association, pp. (110)2, 205-214

Mathews, R. (2023). ‘The effect of cereal Β‐glucan on body weight and adiposity: A review of efficacy and mechanism of action’, Critical Reviews in Food Science and Nutrition, (63)19, pp. 3838–3850

Schuster, J. et al. (2015). ‘Effects of oats on lipid profile, insulin resistance and weight loss’, Nutr Hosp. (32)5, pp. 2111-2116