Are Overnight Oats Good for Weight Loss? A Singapore Guide to a Lighter Jar

By 胖胖 / ResetWith · Updated 24 October 2026

Are overnight oats good for weight loss? They can be: oats are a wholegrain, and HealthHub says wholegrains can help you manage your weight by keeping you full for longer. But what you stir in decides the total. A jar of 50 g rolled oats with low-fat milk, Greek yoghurt, chia and half a banana comes to about 428 kcal by my calculation; add honey and peanut butter and it is about 653 kcal.

I once weighed over 100 kg and lost 34 kg in four months. That is my own experience, not a promise or a target; every body is different.

Are overnight oats good for weight loss?

Overnight oats can fit a weight-loss plan: they are a wholegrain breakfast that HealthHub links with feeling full for longer, as long as the jar fits your daily calories.

Overnight oats are raw rolled oats soaked in milk or yoghurt in the fridge. The Singapore Heart Foundation’s recipe soaks them for at least 2 hours or overnight, so there is no cooking.

HealthHub explains that wholegrain foods are higher in fibre, which adds bulk, and are generally digested more slowly, prolonging fullness. Beta-glucan is a soluble fibre in oats; HealthHub notes it has been shown to help lower cholesterol when eaten regularly.

Overnight oats are not a fat-burning food; any benefit comes from what the jar replaces and how it fits your day.

How many calories are in overnight oats?

In my two example jars, the oats add about 190 kcal and the totals range from about 428 to 653 kcal, so the toppings make the difference.

HealthHub counts ⅔ bowl (50 g) of uncooked oats as one serving of wholegrains. Using USDA values per 100 g, here is what each ingredient adds:

My own calculation from USDA FoodData Central (SR Legacy) values per 100 g; hypothetical jars, not a prescription.

For scale, HealthHub gives an average recommended daily intake of 2,200 kcal for men and 1,800 kcal for women in Singapore. Jar A also gives about half of the 20 g of fibre a day recommended for women (26 g for men).

What does research say about oats and weight loss?

Research suggests cereal beta-glucan, a soluble fibre found in oats and barley, has a small effect on weight: a 2019 meta-analysis of 20 trials found about 0.77 kg lower body weight.

• A 2019 meta-analysis of 20 randomised controlled trials found cereal beta-glucan lowered body weight by 0.77 kg and BMI by 0.62 points on average, with no significant effect on waist circumference or energy intake. Two co-authors were based in Singapore (Singapore Clinical Research Institute and Duke-NUS).
• A 2016 crossover trial in 48 healthy adults found that people felt fuller after instant oatmeal than after an oat-based ready-to-eat cereal with the same calories, and ate 85 kcal less at lunch. It was funded by Quaker Oats Center of Excellence and PepsiCo R&D Nutrition.

The trials tested cereal beta-glucan from oats or barley in general, not overnight oats specifically, so the soaking method is a convenience rather than a special trick. My guide to dietary fibre and gut health explains more about soluble fibre.

Which oats are best: rolled, quick or instant?

Rolled or quick oats are the better pick, because HealthHub groups them as medium GI while instant oats are high GI.

The glycaemic index (GI) ranks carbohydrate foods from 1 to 100 by how quickly and how much they raise blood glucose. HealthHub’s GI table of common foods groups oat products like this:

• Low GI (0–55): oat bran, muesli
• Medium GI (56–69): rolled oats, quick oats
• High GI (70–100): instant oats

HealthHub also says any type of oatmeal, whether steel-cut, rolled or instant, is a healthier choice, but advises avoiding flavoured versions that can contain a lot of sugar. My article on low-GI diets covers what GI can and cannot tell you.

How do I make overnight oats for weight loss?

Start with one serving of plain rolled oats, add a protein source and fruit, and keep high-calorie toppings small.

1. Oats: 50 g plain rolled oats (one HealthHub wholegrain serving). Look for the Higher in Wholegrain Healthier Choice Symbol.
2. Liquid and protein: low-fat milk or plain yoghurt. HealthHub suggests adding low-fat milk or yoghurt, topped with fruit, nuts and seeds.
3. Fruit: half a banana, berries or diced papaya for sweetness instead of syrup.
4. Small extras: a teaspoon of chia seeds or a few nuts. Weigh nut butter and honey; 30 g of peanut butter alone is 179 kcal.
5. Soak: cover and refrigerate for at least 2 hours or overnight.

The Singapore Heart Foundation’s version uses 50 g rolled oats per person (100 g for two) with milk, berries, banana, chia and 40 g of unsalted nuts each, and comes to 374 kcal, 13.1 g protein and 10 g fibre per serving.

Ready-made jars and café versions may use sweetened yoghurt, syrups or generous toppings, so check the nutrition label or ask. For a filling breakfast, protein matters too; see my guide to protein intake during fat loss.

Are there any downsides to overnight oats?

The main downsides are hidden calories from toppings and bloating if you add a lot of fibre too quickly.

HealthHub warns that eating much more fibre too quickly may cause gas, bloating or constipation, so build up gradually. My Healthy Plate advises people trying to lose weight not to cut out food groups but to reduce overall portion size and stay active.

If you have diabetes, kidney disease or another condition, are pregnant, or take medication, speak to your doctor or dietitian before changing how you eat. Do not change your medication on your own. Weight-loss drugs and injections are a decision to make with your doctor.

Frequently asked questions

Are overnight oats good for weight loss?

They can be. Oats are a wholegrain, and HealthHub says wholegrains help manage weight by keeping you full for longer. Keep toppings such as honey and nut butter small, because they can add more calories than the oats.

How many calories are in a jar of overnight oats?

About 428 kcal for 50 g rolled oats with low-fat milk, Greek yoghurt, chia and half a banana, and about 653 kcal with added honey and peanut butter, based on my calculation from USDA values.

Can I use instant oats for overnight oats?

You can, but HealthHub groups instant oats as high GI, while rolled and quick oats are medium GI. Choose plain, unflavoured oats.

How much oats should I eat for weight loss?

HealthHub counts 50 g of uncooked oats (⅔ bowl) as one serving of wholegrains, and the Singapore Heart Foundation’s overnight oats recipe uses 50 g per person.

This article is general health education, not medical advice or a diagnosis. If you have a medical condition, take medication, or are considering weight-loss drugs, please speak with your doctor.

简中摘要

隔夜燕麦(overnight oats)适合减重吗?可以,但关键在配料。燕麦是全谷物,HealthHub 指出全谷物纤维较高、消化较慢,能让人饱得更久,有助体重管理。按 USDA 数据计算,50 克燕麦约 190 千卡;加低脂牛奶、希腊酸奶、奇亚籽和半根香蕉约 428 千卡,再加蜂蜜和花生酱约 653 千卡。2019 年一项统合分析(20 项随机对照试验)发现谷物 β-葡聚糖平均让体重减少约 0.77 公斤,效果不大。HealthHub 把燕麦麸和 muesli 列为低 GI,传统燕麦片和快熟燕麦为中 GI,即食燕麦为高 GI,并建议避免加味燕麦。HealthHub 以 50 克生燕麦为一份全谷物。纤维请逐步增加,以免胀气。有慢性病或在服药者,请先咨询医生。

References

1. HealthHub (HPB). Tips for successful weight management (last reviewed 28 October 2025).
2. HealthHub (HPB). Energy-boosting wholesome breakfasts (last reviewed 27 June 2025).
3. HealthHub (HPB). Boost your health: the essential benefits of dietary fibre (last reviewed 27 June 2025).
4. HealthHub (HPB). The GI values of common foods (last reviewed 26 June 2025).
5. HealthHub (HPB). My Healthy Plate: Eat more.
6. Singapore Heart Foundation. Overnight oats (recipe by Lim Kiat, Senior Nutritionist).
7. U.S. Department of Agriculture. FoodData Central, SR Legacy (2019): oats 173904, 1% milk 170872, Greek yoghurt 170903, chia seeds 170554, banana 173944, honey 169640, peanut butter 172470.
8. Rahmani J, et al. Effects of cereal beta-glucan consumption on body weight, body mass index, waist circumference and total energy intake: a meta-analysis of randomized controlled trials. Complement Ther Med. 2019;43:131-139. PubMed 30935520.
9. Rebello CJ, et al. Instant oatmeal increases satiety and reduces energy intake compared to a ready-to-eat oat-based breakfast cereal: a randomized crossover trial. J Am Coll Nutr. 2016;35(1):41-9. PubMed 26273900; full text, PMC4674378.