Fats are not all bad—in fact, quite the opposite! Some are key for a healthy heart, good digestion, proper brain function, a strong immune system, nice skin, and even for weight loss.
But attention! Not all fats are equal. And the amount matters too. In this article, we’ll reveal why we need fats, what happens if we get too little, and which signs warn us that we’re in the red zone.
Why do we need fats at all?
Fats, along with proteins and carbohydrates, are one of the three main sources of energy. They have an interesting property: 1 gram of fat gives 9 calories, while carbs and proteins only have 4 calories per gram.
This means fats are an efficient energy source that keeps us full for longer. And that’s not all. They also help with:
- building cell membranes, i.e. the protective envelope of cells,
- absorbing vitamins A, D, E, and K, which are only soluble in fat,
- hormonal balance (especially important for women),
- brain function, since about 60% of the brain is made of fatty acids.
The body cannot make certain essential fatty acids (e.g. omega-3 and omega-6) on its own, so we must get them from food.
What happens if you eat too few healthy fats?
First: What exactly are healthy fats? Mostly unsaturated fats, which are found in fish (salmon, sardines, mackerel), nuts, seeds (flaxseed, chia), avocado, olive oil, and eggs. Bad fats are mostly trans fats (found in processed foods) and saturated fats, which are abundant in fried and fatty animal foods (salami, sausages, butter, etc.).
And now the key question—how do we know if we’re getting too little?
If you eat too few healthy fats, very specific signs can show up, which we often mistake for other problems. Here’s what research and experts say:
- You just can’t lose weight, even though you try
It might seem illogical, but a study published in the American Journal of Clinical Nutrition showed that people who got less than 20% of their daily calories from healthy fats lost weight slower than those who ate more healthy fats. Why? Fats make us feel full, slow down stomach emptying, and reduce hunger.
So, if you’re always hungry and make no progress with weight loss—this could be a clear sign your body is missing the right fats. - You’re constantly hungry, even after a meal
If after a big lunch you’re already eyeballing the fridge half an hour later, something isn’t right. One possible reason is your meal lacked healthy fats, which would slow down digestion and balance blood sugar.
A study at Harvard School of Public Health showed that a diet rich in unsaturated fats reduces the need for snacks by up to 30%! - Your skin is dry, cracked, and dull
Skin cells are surrounded by a protective layer of fatty acids. If you lack them, your skin becomes dry, itchy, and sensitive to external factors. Even the best cream won’t help if the body doesn’t have the building blocks from within to nourish the skin.
Omega-3 fatty acids are especially important—a 2018 study showed that after just 12 weeks of omega-3 supplementation (in the form of flaxseed oil), skin became 39% more hydrated. - You feel tired and low on energy
The heart gets about 70% of its energy from fats. If there aren’t enough, the body turns to a less efficient fuel—carbohydrates. And since those give energy quickly but take it away even faster, the result is the well-known energy crash.
Fats are also essential for the function of mitochondria, the cell’s “power stations”, where energy is produced. If mitochondria are undernourished, tiredness is inevitable. - You can’t concentrate, you’re forgetful and lack focus
As mentioned—the brain is 60% comprised of fats. If you lack them, it affects nerve transmission, focus, learning, and even memory.
A study at the University of Illinois showed that a diet with enough monounsaturated fats (e.g. olive oil, nuts) improves working memory by as much as 20%. Additionally, omega-3 fatty acids are linked to a lower risk of dementia and Alzheimer’s disease. - You’re always cold—even in a warm room
Fat tissue isn’t just a reserve; it’s also thermal insulation. If you have too little subcutaneous fat (not necessarily related to how thin you are), you’ll feel cold more easily. The body loses heat faster if it has no protective layer.
That’s why women naturally have a higher percentage of body fat (between 20 and 30%) than men (between 10 and 20%). This layer isn’t about looks—it’s natural protection against the cold and hormonal changes.
So, what can you do?
First—don’t be afraid of fats. Be afraid of the wrong fats and wrong quantities. According to WHO (World Health Organization) recommendations, daily fats should provide between 20 and 35% of your daily calories—so, at 2000 calories per day, that’s somewhere between 400 and 700 calories from fats (which means about 44 to 78 grams of fat daily).
The ratio is important:
- over 80% should be unsaturated fats (from plant sources, fish, nuts),
- less than 10% should be saturated fat (butter, milk, cheese),
- trans fats should be less than 1%—basically almost nothing.
Listen to your body
If you’re constantly tired, dry, irritable, hungry and can’t lose weight, don’t look at calories first—look at your fats. They’re like oil in an engine—if you have too little, the car will break down, even if you put in plenty of petrol.
As the famous American nutritionist Dr. Walter Willett once said: “Fats aren’t the enemy. They’re fuel. We just have to know which oil is right for our body.”
P.S.
If you’re not sure if you’re eating enough healthy fats, try one week on a diet rich in omega-3s (e.g. a tablespoon of flaxseed oil, a handful of walnuts and a piece of salmon twice a week)—and watch the difference. You’ll notice it very quickly...
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