Diet: reduce fat or carbohydrate?

If you are trying to lower calorie intake for better weight loss, you will probably ask a question at some point: is it better to cut fat or carbohydrate calories? This is what this articles is about and I start with probably somewhat surprising answer. Actually, two answers because they are different for diet in general and diet for weight loss and exercise:

For general nutrition, cut down on carbohydrate first, especially refined sugars and starch products. It is very likely that you are overeating particularly these kinds of carbohydrate, which have proved to be most detrimental to human metabolism.

For weight loss and exercise, it does not matter if you cut down on fat or carbohydrate or both, as long as you:

  • Supply essential fatty acids as 1-2 serving of unsaturated fats (oils);
  • Supply sufficient protein to maintain and build muscle: preferably, at least 1 grams protein per kg body weight.

Lets get into detail on how I arrived to this answer.

The 2010 nutritional guidelines by US government call or the following proportion of energy (calorie) intake for adults:

CarbohydrateProtein:Fat:
45–65%10–35%20–35%

As we can see, this diet is biased in favor of carbohydrate. Is this something that is based on research or something that merely reflects our habits?

Talking about out real habits, take a look at the graph of soft drink consumption here(from here):

The soda sales in US have pretty much hit the ceiling but in developing countries, which strive to live by “western” standards, sweet water sells pretty well. Coca Cola spends about 10% of its 12 billion profits on advertisement and it goal is to double business by 2020, mostly by growing in developing world.

In soft drinks sold in US, carbohydrate comes in a form of HFCS – high fructose corn syrup. It is a mixture of sweet simple sugars glucose and fructose obtained by chemically processing corn. Fructose is very sweet, it is sweeter than regular sugar (sucrose), which is one reason for using HFCS. Another reason is price – HFCS is cheap because US companies get subsidies to grow corn, or else cheaper foreign sugar made of sugar cane would put them out of domestic market.

Not only we mostly replace water with soft drinks, but we have also created negative image for water consumption. Many people think that tap water is somehow inferior in quality to bottled water, which is a misconception. About half of bottled water sold is nothing but a regular tap water. If you go to any fast food place, you will be offered a huge 24 or 32 oz brightly colored cup for soft drink (free refills, of course). If you ask for water, you well be offered a tiny inconvenient 8 oz cup. Not enough for a hot Texas day! 32 oz cup of soft drink is, by the way, 4 servings – about 400 calories with absolutely no essential nutrients.

The map of soft drink consumption in US is a pretty good overlap with a map of obesity and heart disease. Here is my article about that. This is not surprising since every known metabolic marker is affected by high carbohydrate consumption. Glucose tolerance is reduced, “bad cholesterol” (smaller LDL) rises, good cholesterol (HDL) drops, and fats (triacylglyceroles) also rise. Yes, you are reading this right – high carbohydrate in diet raises fat level in blood. This leads to diabetes, obesity and elevated risk of heart disease.

There are generally three problems with carbohydrate rich foods:

  • Too high on calories. Just an example: a 4 oz chocolate muffin has 8g protein and 360 calories. 4oz of pork have 28g protein and 280 calories.
  • Too high in simple sugar (glucose), causing a blow to your metabolism by messing up glucose balance. Note that starch is also glucose but connected in a chain: in your stomach and small intestine, it is digested and absorbed into blood as glucose.
  • Too low on essential nutrients. Companies are trying to get around this by adding things like vitamin C and labeling it “Vitamin Water” but it does not make no difference – it still over 100 calories, and still no protein. You can easily get you daily dosage of vitamin C from real fruits and vegetables, like onions and oranges. The problem of course is that real stuff is not as sweet and that is why so many people prefer varous forms of sweet water labeled as “juice”.

Fat, especially fat from meat and diary products (solid, or saturated fat) has been getting negative publicity. It is easy to convince people that fat is bad if you tell them that fat is what makes them “fatter”. So many people are looking for “zero saturated fat” products and often replace them with foods rich in carbohydrates. Our body can easily convert fat to carb and carb to fat in a snap. What really matters is the total amount of consumed calories. Unused calories from either source will be saved as fat, mostly in abdominal area.

In 2010 analysis, some prominent experts in a field, Ronald Krauss and colleagues, have reached a conclusion that there was “no significant evidence that dietary saturated fat is associated with an increased risk of cardiovascular disease”. However, increasing consumption of polyunsaturated fat is independently associated with reduced risk of cardiovascular disease. The take home message: you can have nutrition rich in saturated fats (meat, diary products, eggs), but be sure to also include products rich in polyunsaturated fats: fish and plant foods. Replacing saturated fat with carbohydrate is a bad idea.

All above is described for diet unrestricted in calories and for those who do not take steps to include exercise and/or increase their activity level. For an individual with an average genetic makeup, eating as much as you want and not exercising will result in a slow weight gain, slow muscle loss, and all chronic diseases that come with it. This will happen regardless of what you are eating. Under those conditions, lowering carbohydrate to a minimum, reducing saturated fats, and increasing unsaturated fats is a good idea, but it will only slow down the process of slow decrease in fitness. With these diet modifications, expect better weight control and about 30% decrease in the risk of cardiovascular disease.

But things are a little different when calories are restricted. When calories are down to about 70% (1400 kcal), both low fat / high carb and high fat / low carb diets worked about equally well. Low high fat / low carb diet showed slightly more of weight loss (9.2% vs. 7%). In both diets, cardiovascular markers were also improved: lower fat (triacylglycerol) level, higher “good cholesterol” (HDL) and lower “bad cholesterol” (small LDL).

So the take home message is:

it is not the particular fat to carbohydrate ratio that matters, but the total amount of consumed calories.

With calorie restricted diet alone, both loss of fat tissue and loss of muscle tissue will occur, accompanied by a decrease in metabolic rate – body’s ability to burn food into energy. This is described in more detail here. For both weight loss and increase in fitness level, diet needs to be combined with an exercise regime and an increase in low-level and moderate-level activity. When combined with exercise, very different types of diets give significant improvement in all health parameters, but high protein / low carbohydrate diet allows for better muscle gain and better fat loss.

Here is an example of how diet and exercise combinations worked for obese women (average weight 94 kg, BMI 34.9) over 14 weeks:

RegimenDietWaist size change, cmBody mass change, kg
Exercise + 1200 kcal diet63% protein, 7% carbDecrease by 6.3Decrease by 5.6
Exercise + 1200 kcal diet50% protein, 20% carbDecrease by 6.7Decrease by 6.5
Exercise + 1200 kcal diet15% protein, 55% carbDecrease by 5.7Decrease by 4.0
Exercise only, no dietNormalDecrease by 5.1Decrease by 0.2
No exercise, no diet (control)NormalIncrease by 8.2Increase by 1.4

(from Kerksick, 2009).

I marked best results I bold. Clearly, limiting calories, keeping protein high and carbohydrate low gives best results for weight loss in combination with exercise. Also note two other things: 1) No exercise, no diet group got significantly fatter over 14 weeks and 2) Exercise only also gave small, but visible improvement.

In summary, for exercise and weight loss, the total amount of calories and amount of protein is more important than a fat to carbohydrate ratio. As long as you keep calories low, weight loss will occur. High protein, on the other hand, will facilitate muscle gain.

Whether you are focusing on lowering carbohydrate or lowering fat, there is a couple of things to remember:

  • Refined sweet sugar (sucrose and HFCS) is extremely unhealthy and mess up metabolism. It should be avoided at all cost.
  • Daily need for essential fatty acids must be met. This can be easily done with 1 to 2 servings of regular cooking oils such as canola oil and vegetable (soybean) oils. There is no scientific basis for providing more than necessary amount of omega-3 fatty acids in a form of supplements (flax seed, fish oil, etc.).
  • It helps to increase protein to above the recommended daily amount to retain and build muscle: 1 gram per kilogram body weight or more. If you are more into muscle building (“bodybuilding”), then go up to 2 grams per kilogram, or 1 g per pound. You cannot overeat on protein – whatever is not used as building material will be used as energy source.

When you decide to limit calories there is a practical consideration though: most animal protein sources are rich in fat calories and low on carbohydrate. This means that if you build your diet around these products, you will quickly max out your calories, and there will be little or no space left for carbohydrate products. This is exactly how I build my diet – around meat, eggs, milk, poultry and fish. I really do not mind dumping most carbohydrate. My staple food is meat, mostly trimmed pork, and eggs – two per day. I call is a “caveman’s diet”. My full article about it is here.

I personally use a “carbohydrate avoidance strategy” – for me, this is the easiest way to limit calories. This means no sugar in the house, no soft drinks, no sweet stuff, no bread, grains limited. But there is an advantage to it also – I can enjoy an occasional sausage (200 kcal) or a beer (another 200 kcal). I do get some carbohydrates from vegetables though – mostly potatoes. I found that this approach works great and is very easy to maintain, I only need to buy a few very basic foods in a grocery store.

Advanced reading:

Saturated fat, carbohydrate, and cardiovascular disease.
Siri-Tarino PW, Sun Q, Hu FB, Krauss RM. Am J Clin Nutr. 2010 Mar;91(3):502-9.

Meta-analysis of prospective cohort studies evaluating the association of saturated fat with cardiovascular disease.
Siri-Tarino PW, Sun Q, Hu FB, Krauss RM. Am J Clin Nutr. 2010 Mar;91(3):535-46.

Metabolic effects of weight loss on a very-low-carbohydrate diet compared with an isocaloric high-carbohydrate diet in abdominally obese subjects.
Tay J and others. J Am Coll Cardiol. 2008 Jan 1;51(1):59-67.

The role of reducing intakes of saturated fat in the prevention of cardiovascular disease: where does the evidence stand in 2010?
Astrup A and others. Am J Clin Nutr. 2011 Apr;93(4):684-8

A randomized trial of a hypocaloric high-protein diet, with and without exercise, on weight loss, fitness, and markers of the Metabolic Syndrome in overweight and obese women.
Meckling KA, Sherfey R. Appl Physiol Nutr Metab. 2007 Aug;32(4):743-52.

Effects of a hypocaloric, low-carbohydrate diet on weight loss, blood lipids, blood pressure, glucose tolerance, and body composition in free-living overweight women.
Meckling KA and others. Can J Physiol Pharmacol. 2002 Nov;80(11):1095-105.

Effects of a popular exercise and weight loss program on weight loss, body composition, energyexpenditure and health in obese women.
Kerksick C and others. Nutr Metab (Lond). 2009 May 14;6:23.

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