Will eating more fat make me gain weight?

In short, no. Eating more fat will not make you gain weight.

In fact, including fats in your diet can help you lose weight, if that’s important to you.

I appreciate that at face value, this might not make a lot of sense, but hopefully it will become clearer as we dive deeper into the science.

It’s important to acknowledge that if you're eating an excess (i.e. more than your body needs) of dietary fat, then yes, you could gain weight. But, this is true if you're eating an excess of any macronutrient or food because ultimately it's the excess energy that causes you to gain weight, not the specific type of nutrient.

So if this is the case, why are people so worried about fats in particular?

Well, fats have more energy (or calories) per gram than carbohydrates or protein, which can lead to the fear that eating fats will have a greater contribution to weight gain. But, if you’re mainly focusing on the inclusion of unsaturated, nutrient-rich and minimally processed fats (e.g. olive oil, nuts, seeds, avocado and fish), then this isn’t necessarily true for a couple of key reasons:

1. Not all of the energy stored in these foods is actually available or accessible to the body.

Let’s take nuts as an example. We know from research carried out by our very own Prof Sarah Berry that ~30% of the energy in nuts isn’t absorbed by the body and so doesn't contribute towards body fat stores.

2. Dietary fats can support satiety.

Including a portion of higher-quality fats in your meals can help you feel fuller for longer, meaning that you’re more likely to feel satisfied after your meal and less likely to overeat later on.

3. Fats taste good.

While feeling that physical fullness can help to reduce overeating, feeling emotionally satisfied is also important. Fats are full of flavour and can be responsible for adding creaminess, texture and flavour to our meals, contributing to our enjoyment of that eating occasion. If we enjoyed our meal, we're less likely to go in search of something else soon after eating.

Research has shown that fats don’t make us fat time and time again. There’s a trial showing that either a low-fat or low-carb approach can result in weight loss, as both are simply different ways to reduce overall energy intake.

There’s also plenty of research demonstrating that dietary patterns typically high in fat, like the Mediterranean diet, can lead to significant reductions in body weight.

Aside from just not wanting to fear fats, there are also so many reasons that we should embrace them! They’re essential for a multitude of bodily functions and processes, including:

Overall, eating fat in moderation as part of a balanced and healthful eating approach isn’t going to make you gain weight. We need fats in our diet to remain healthy, but it can be a good idea to focus on including more of those nutrient-rich sources like fish, avocado, olive oil, nuts and seeds, and try to reduce your intake of the less nutrient-rich options like processed meats, fried foods, pastries and so on.

There’s of course space for all foods in a healthful eating approach, but there are naturally some things we might want to include more of than others to best support our health.