Low Fat Diets: why they work and why they don’t…

Why low fat diets actually work and why they aren’t good for you.

In the first part of this blog we will be looking at low fat diets. Unless you’ve been hiding under a rock for the past 50 years you would’ve heard an abundance of crazy diet guidelines (including from government backed schemes – pyramid diet anyone?). You may have even tried a few of them (ALL of my clients have tried more than 5 at least). Why are they useful and spoken about so much and what can you do to avoid dieting ever again and actually maintain your ideal physique?

The diet industry is worth billions upon billions each year because women (and men) all over the world continue to start, stop and start diets again and again and again. Therefore diets are always making money. Just think how much money you’ve spent on various diets and are you where you want to be right now after spending so much? So what can you do to avoid this process of repeatedly doing something that’s never actually worked for you (you may have gotten results on a specific diet but if you need to start again and again then is it ‘really’ successful?

In this first part we’re going to talk about Low Fat diets.

Low Fat…

Why it works

The whole goal of fat loss suggests that fat is not a good thing for our bodies. However, this has very little to do with dietary fats and there are plenty of ‘essential fats’ that the body actually needs through the diet because they cannot be made by the body. Cutting fat out of your diet actually helps to reduce calories because 1g of fat = 9calories so if you cut your fat out or even just reduce it by as little as 20g per day that would mean you may actually be reducing your calories by at least 180 calories per day. Therefore replacing 10% of the diet with carbohyrdates (or proteins) will reduce the total calories of the diet.

However, the effects of a low fat diet are uncertain when reviewed over the longer term (Katan, Grundy, Willett. 1997).

Why it doesn’t work

However, numerous research has shown that essential fatty acids really are essential therefore cutting these out of your diet may cause health problems further down the line (SUCH AS…) “Low-fat,” “reduced fat,” or “fat-free” processed foods are not all that healthy. One problem with a generic lower-fat diet is that it prompts most people to stop eating fats that are good for the heart and essential for the body.

Fats and your Heart

High fatty diets have been associated with high cholesterol and poor heart health within the media. However, most research simply doesn’t support a low fat diet to make any improvement in cholesterol levels or heart health. In fact, research have shown that increasing good fats (unsaturated) in favour of carbohydrates, actually decreases the amount of cholesterols in the blood.

In trials in which polyunsaturated and monounsaturated fats were eaten in place of carbohydrates (increasing the percentage of calories from fats), these good fats decreased levels of harmful LDL and increased protective HDL. (Mensink R, Zock P, Kester A, Katan M. 2003) More recently, a randomized trial known as the Optimal Macronutrient Intake Trial for Heart Health (OmniHeart) showed that replacing a carbohydrate-rich diet with one rich in unsaturated fat, predominantly monounsaturated fats, lowers blood pressure, improves lipid levels, and reduces the estimated cardiovascular risk. (Appel et al. 2005.)

Unsaturated fats are called good fats because they can improve blood cholesterol levels, ease inflammation, stabilize heart rhythms, and play a number of other beneficial roles. Unsaturated fats are predominantly found in foods from plants, such as vegetable oils, nuts, and seeds. They are liquids at room temperature.

There are two types of unsaturated fats:

  • Monounsaturated fats are found in high concentrations in olive, peanut, and canola oils; avocados; nuts such as almonds, hazelnuts, and pecans; and seeds such as pumpkin and sesame seeds.
  • Polyunsaturated fats are found in high concentrations in sunflower, corn, soybean, and flaxseed oils, and also in foods such as walnuts, flax seeds, and fish; canola oil, though higher in monounsaturated fat, is also a good source of polyunsaturated fat. Omega-3 fats, which are fast becoming the darling of the supplement industry, are an important type of polyunsaturated fat. The body can’t make these, so they must come from food.


Omega-3 is one of 3 different types of omega fats including omega-6 and omega-9.

Some of the best sources of Omega-3 include flaxseeds and walnuts, along with different oils such as flaxseed, canola, soybean, walnut, and wheat germ. Omega-3 fatty acids can be found in smaller quantities in nuts, seeds, and soy products, as well as in beans, vegetables, and whole grains. Corn, safflower, sunflower, and cottonseed oils also contain omega-3s, though in lower levels than the previously mentioned oils.

Plant Foods Rich in Omega-3 Fatty Acids

  • Ground flaxseed
  • Walnuts
  • Soybeans
  • Mungo beans: Mungo beans are particularly high in omega-3 fatty acids. They are sold in many Indian groceries and may be found under the name “urid.”

Omega-3 Content of Natural Oils

  • Flaxseed 53-62%
  • Linseed 53%
  • Canola 11%
  • Walnut 10%
  • Wheat germ 7%
  • Soybean 7%

Flaxseed oil and ground flaxseeds are particularly good choices to meet your needs for omega-3 fatty acids. One teaspoon of flaxseed oil or one tablespoon of ground flaxseed will supply the daily requirement of ALA. Flaxseeds must be ground in order for you to absorb the proper nutrients, and flaxseed oil or ground flaxseeds are best stored in the fridge to maintain freshness.

The ratio of omega-6 to omega-3 has been spoken about a lot within the inner circles of the fitness industry as the typical western diets close to a ratio of 35:1 in favour of omega-6. However, recent research has suggested the desired ratio to be closer to 5:1 (1gram of omega-3 for every 5grams of omega-6).

Instead of worrying about counting grams of omega-6 and omga-3 I would simply look to increase the foods mentioned above containing omega-3 and reduce the food containing omega-6 particularly vegetable oils and cook with coconut oils if needed. Krill oil (1:10) and Fish oils (1:7) have the greatest omega-6 to omega-3 to omega-6 ratio in favour of okega-3. Therefore, introducing these into your diet could improve your diet and omega ratios.


Omega-6 fats are derived from linoleic acid and are found in leafy vegetables, seeds, nuts, grains, and vegetable oils (corn, safflower, soybean, cottonseed, sesame and sunflower).

These foods are normally well maintained in the western diet that will allow for an abundance of omega 6 into the persons diet.

However, when fat is eliminated from the diet this can cause a deficiency in omega-6. As omega-6 is important for cell growth (think cell regeneration and repair) omega-6 deficiencies can affect the brain and quality of muscle (decreasing your metabolism) and hormonal balance.

Omega-6 plays a critical role in the production of hormone like messengers called PGE1 that trigger immune responses, reduce fluid build-up whilst also impacting mental state such as depression, PMS, mood swings, schizophrenia, ADHD and multiple sclerosis.


Therefore, it could be concluded that although replacing fat with carbohydrates lead to a reduced calorie intake this can actually increase cholesterol (Mensink, Zock, Kester, Katan 2003). So whilst weight may be lost a better alternative may be to simply lower your overall calorie intake (or simply decrease the portion sizes of your meals) over all macro-nutrients (Carbohydrates, Fats and Proteins).

In the next episode we will be talking about the effects of a low carbohydrate diet.

As always if you have ANY questions please comment below and I would be more than happy to answer any and all of your questions.



Appel L, Sacks F, Carey V, et al. “Effects of protein, monounsaturated fat, and carbohydrate intake on blood pressure and serum lipids: results of the OmniHeart randomized trial.”  JAMA. 2005;294:2455-64.

Katan MB, Grundy SM, Willett WC. “Beyond low-fat diets.” N Engl J Med1997;337:563–6.

Mensink R, Zock P, Kester A, Katan M. “Effects of dietary fatty acids and carbohydrates on the ratio of serum total to HDL cholesterol and on serum lipids and apolipoproteins: a meta-analysis of 60 controlled trials.” Am J Clin Nutr. 2003;77:1146-55.

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