Can fats make us thin?

Could healthy fats be the key to weight loss?

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Qualified Nutritionist (BSc, MSc, RNutr)
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12 October 2017

An intro to the demonisation of fats

For many years fats have been demonised. We were advised to eat less fat and as a result, ‘low fat’ products were all the rage (and worrying still are to some extent). These proved especially popular with people on a diet or those trying to lose weight.

However, it seems that avoiding fats may not actually be the best approach if you’re working hard to maintain a healthy weight, and there’s research out there to back this up. 

There are lots of considerations when it comes to fat intake; firstly if we are eating less fat what are we eating instead? Then, we have all the effects of fats on our appetite and metabolism, which we need to consider too! Let me explain.

Energy balance and satiety

When it comes to fats, they are the most energy-dense macronutrient out there providing 9kcal/g. So initially, there may be some reason to believe that we need to watch our fat intake if we are trying to lost weight, however, I want to throw a little spanner in the works here with some food for thought.

If we eat ‘low fat’ foods, what are we actually eating instead? There are only 4 main macronutrients available, so low fat, most likely means higher carbohydrates. Increasing your intake in carbs, and ultimately sugar, certainly isn’t going to have very favourable effects on your waistline! 

So, this really is something to consider when you’re reaching for that low-fat variety – what has the fat been replaced with? In most cases I can guarantee it isn’t good quality protein! Also, ultimately, it means the product is more processed too – you can guarantee the ingredients list is longer and more chemical-looking, which can throw your body into further turmoil.

Next, we need to consider satiety – that is, what makes us full. I’ve discussed the issues with sugar and carbohydrates before – we know that they can cause havoc with our blood sugar causing peaks and troughs in insulin which ultimately, can make us hungrier in the short-term (plus bigger concerns in the long-term!). And research has shown that protein1 and good quality fats2,3,4,5 instead, may help to keep us fuller for longer – go figure!

What are the mechanisms for fats and appetite

Now, not to get too technical, but I want to explain a little around how fats can help to keep us fuller for longer. 

Fat, when compared to the other nutrients, take longer to empty from the stomach.  This means we are more likely to feel fuller for longer! 

However an added benefit is that including some fat in your meals can also help to delay the uptake of other macronutrients such as sugar. So, if you ingest a lovely balanced meal, that is with some nice fats, protein and complex carbs (hopefully some fibre in there too), the simple sugars units making up the carbohydrate portion will be forced to be more slowly absorbed  into the blood stream. This means that the effects on our blood sugar, insulin responses and ultimately our appetite, won’t be so severe but much more gradual instead!

So, the result of having a fuller tum for longer, gentler effects on blood glucose together with a unique activation of chemical messengers in the gut6, it seems you’re much less likely to experience your next hunger pang so quickly after eating a meal infused with some nice fats.

What about metabolism

Fats are extremely important for manufacturing many important hormones in our body too. And hormones? They’re extremely important for keeping us lean! An imbalance in hormones, for example during the menopause or PCOS can cause havoc with our weight as so many women know only too well.  

Then, we have the more direct effects of the food we eat on our hormones. We know that carbohydrates prompt the release of insulin, but interestingly fats (in their purest form that is!) don’t. Now, insulin is responsible for clearing our blood glucose and putting glucose into storage form, glycogen, inside our fat cells. So a constant high of insulin means we are technically in fat-storing mode. However, with the intake of healthy fats instead, we aren’t releasing so much insulin and this means we are more likely to be using our stores for energy!

Olive oil specifically

Some new exciting research has looked at why olive oil may have additional, unique properties, meaning it may be able to help support our weight even more so, than some other healthy fats. A major part of the well acclaimed Mediterranean diet, this important ingredient shouldn’t be shunned by those looking to lose weight, which makes perfect sense – those lean Mediterranean people certainly aren’t scrimping! In fact, for many of the healthiest communities in the world, healthy fats are a big part of the diet, think good quality oils, oily fish, nuts and seeds – no need to be counting calories here!

It seems that olive oil rich in the polyphenol oleuropein (which we already know has beneficial effects on our cardiovascular system) may also have beneficial effects on our insulin responses7. Better insulin and blood sugar control ultimately means better weight management which all sound very promising to me.

What’s my advice when it comes to fat intake?

Not all fats are equal of course so we still need to stay clear of fast food joints and fat-laden processed meals. But we shouldn’t be scared to include good quality fats such as olive oil, coconut oil, avocados, oily fish, nuts and seeds in our diet as it turns out, they could help you in your weight loss efforts! Remember, all of these came from nature and are rich in naturally occurring vitamins and minerals too (plus as an added bonus fats actually help support the absorption of many vitamins and minerals) which also help support your metabolism. Yet again, eating fresh is key, so try not to be so tempted by all those ‘low-fat options in future!


1. Westerterp-Plantena MS, Lemmens SG and Westerterp KR.. Dietary protein – its role in satiety, energetic, weight loss and health. Br J Nutr, 2012, 108 Suppl 2:S105-12

2. Maljaars J et al. Effect of fat saturation on satiety, hormone release and food intake. Am J Clin Nutr, 2009, 89(4), 1019-1024

3. Parra D et al. A diet rich in long chain omega-3 fatty acids modulates satiety in overweight and obese volunteers during weight loss. Appetite, 2008, 51(3), (676-680)

4. Matzinger D et al. The role of long chain fatty acids in regulating food intake and cholecystokinin release in humans. Gut, 2000, 46, (689-694)

5. Buckley JD and Howe PRC. Long-chain omega-3 polyunsaturated fatty acids may be beneficial for reducing obesity – a review. Nutrients, 2010, 2(12), (1212-1230) 

6. Schwatz G, et al. The lipid messenger OEA links dietary fat intake to satiety. Cell metabolism, 2008, 8(4), (281-288)

7. Wu L et al. Olive component oleuropein promotes β-cell insulin secretion and protects β-cells from amylin amyloid-induced cytotoxicity. Biochemistry, 2017, 56(38), (5035-5039) 

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