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Q+A – Fats and Appetite Suppression

July 12, 2011

Q: I definitely understand that protein helps you reach satiety. I learned from your article that carbs will also help control appetite, that’s new to me. Some of the other information I dig into suggests that high quality fats control the I’m full switch in your brain. What’s your take on that on/off switch and having high quality fats in your diet as both an appetite suppressant and fuel source?

A:In terms hunger its not so much an on/off switch as a dimmer controlling a whole strip of lights. There are TONS of different factors involved and some have more effect than others in terms of the “brightness”. The mechanisms of appetite control are extremely complex (I intend to eventually dedicate an entire article to this topic) and not nearly fully understood. You are absolutely correct in saying that fats play a role in hunger regulation. Fat has been show to enhance cholecystokinin (CCK) secretion, which reduces appetite. The CCK response to fat is short lived however (30 min or so) and is also affected by other foods as well. Fats also stimulate a strong response of peptide YY (PYY) release, a peptide that promotes satiety and enhanced nutrient absorption (although proteins and fiber induce a strong response as well). Other mechanisms are involved too, but the general consensus right now is that a mixed meal (containing proteins, carbs, and fats) is optimal.

Having said that, does the quality of the fat increase fullness/suppress appetite? A couple studies have been published in the last year directly comparing saturated fats (commonly in meats, cheeses, dairy, and many spreads), mono-unsaturated fatty acids, MUFAs, (olive oil, almonds, peanuts), and poly-unsaturated fatty acids, PUFAs, (walnuts, fishes) on appetite. One well designed study used breakfast muffins with different types of fats. The muffins contained 26 grams of either saturated, MUFA, or PUFA and was given to 3 different groups of individuals. The study concluded that there was NO DIFFERENCE in hunger, satiety, or daily calorie intake among individuals in the different groups. So, in at least the short term, the “quality” of the fat makes little difference on hunger. Another study compared difference lengths of fats, short (dairy), medium (coconut oil) and long (meats) in a similarly designed test. These breakfasts used a whopping 52 grams of the fats, respectively. Again, no difference was shown in any category related to hunger, satisfaction or calorie intake. Current evidence suggests that the type/quality of fat plays little role in the overall hunger control system. Ongoing research is currently being conducted on pinolenic acid, a long chain fat, because it specifically has been shown to effect hunger more than others. But the mechanisms behind this are currently unknown. It does show that there may be a future in fat quality and hunger, but at least right now, other nutrients play a MUCH larger role.

Please don’t misunderstand however, that there are MANY, MANY studies PROVING the HEALTH BENEFITS of MUFAs and PUFAs and I would always recommend consuming a high percentage of your fats from these “high quality” fats, especially the omega 3 fatty acids (fish, flaxseed, walnuts, supplements, etc)

On to fat as a fuel source… put simply, its the best there is. Fat offers so much energy packed into a small amount that its a great way to reach your total daily calories needs. Beyond that it plays many vital roles in the bodies metabolism. However, there are some things that should be noted about fat being used as an energy source. It is a very long process that your body has to go through to utilize fat as energy. In fact, there are so many steps in the process that when you need a LOT of energy in a short amount of time (like for crossfit training), your body simply cannot process fats fast enough to provide your tremendous energy needs. Carbohydrates can very quickly and efficiently be used as energy. Because of this, carbs will ALWAYS be your primary source of energy for any high intensity training and optimal performance and endurance is not achieved without proper carbohydrate consumption/stores. A diet consisting of ~60-70% carbohydrates yields the best athletic performance and should be the goal before any competition. Fat will be your main energy source when your body needs a nice consistent flow of energy, like the majority of the day or during any low- moderate- intensity exercise you perform (yardwork, walks, casual swimming, hiking, etc). The body very efficiently uses its sources of energy in this way, but utilizing the best source (fat) when it has the time to perform all the steps necessary and preserves the carbs for times when it needs lots of energy in a short amount of time.

Ketogenic diets are a different story all together … I will probably do an entire article or series on that at some point as well.

Piece of Cake .. Nutrition:
Consume ~2 grams of fat per pound of body weight on a daily basis and focus on consuming “high quality” MUFAs and PUFAs especially the omega-3s. (This should yield between 20-35% of your total daily calories, depending on the rest of your diet)

Beglinger C, Degen L. Fat in the intestine as a regulator of appetite–role of CCK. Physiol Behav. 2004;83(4):617–621.
Dunford, Marie, and J. Andrew Doyle. Nutrition for Sport and Exercise. Belmont, CA: Thomson Wadsworth, 2008. Print.
Poppitt, and Et Al. “Fatty Acid Chain Length, Postprandial Satiety and Food Intake in Lean Men.” Physiol Behav Aug 101.1 (2010): 161-67. PubMedCentral. 4 Aug. 2010. Web. July 2011.
Strik CM, Lithander FE, McGill AT, MacGibbon AK, McArdle BH, Poppitt SD. “No Evidence of Differential Effects of SFA, MUFA or PUFA on Post-ingestive Satiety and Energy Intake: a Randomised Trial of Fatty Acid Saturation.” Nutr J 24th ser. 24.9 (2010). PubMedCentral. Web. June 2011.

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