How much fat should you eat when dieting

Does fat make you fat, are fats just necessary to make you fat for times of famine, and how important is testosterone when cutting?

In order to lose weight, you need to be in a caloric deficit – eat less than what you burn. To maintain muscle, exercise performance, a fast metabolism, satiety, protein and carbs are the most important.

So where do fats fit in?
Dietary fats are essential for testosterone production (A), absorption of fat soluble vitamins and it insulates the body organs against shock, promotes cell integrity (saturated fats only) and maintains healthy skin and hair.

More specifically, fats are also able to affect insulin sensitivity, uncoupling (thermogenesis) and mitochondrial biogenesis (production of new mitochondrias).

The thermic effect of nutrients, expressed as percentage of their energy content, is 2–3% for lipids, 6–8% for carbohydrates and 25–30% for proteins. This means that the efficiency of nutrient utilization (calculated as 100%—the thermic effect of the nutrient) is higher for fat than for carbohydratesor protein. Thus, by subtracting the values of the thermic effects from a theoretical 100% efficiency, one obtains an efficiency of energy utilization of 70 – 75% for proteins, 92 – 94% for carbohydrates and 97 – 98% for lipids. Hence, fats are very easily stored as fat, especially when combined with carbs.

Variability in the thermic effect of fat can be attributed to differences in molecular structure that significantly alter its metabolism. For example, Seaton et al. (1) found that medium chain triglycerides (MCTs) produced a significantly greater thermic effect than long chain triglycerides during a 6-hour postprandial period (12 vs. 4% higher than basal oxygen consumption). MCT can actually be used as a fat burning substance (A).

Nutrient energy balance


As the body prefers to burn carbohydrates, fat will be stored when ingested in the same meal. Thus, both the efficiency of fat utilization and the post-ingestive fuel selection of fat indicates that this nutrient has a greater metabolic potential to induce weight gain than dietary carbohydrates or proteins.

Another down side of fats, are that a high-fat diet promotes excessive energy intake by passive overconsumption; the fat-induced appetite control signals are too weak or too delayed to prevent excessive energy intake from a fatty meal. (2) For instance, after eating 3 medium potatoes, you’ll be full, and you will have ingested 500 calories. Now add 1-2tbsp of butter and cream cheese, and you’ll still be able to eat all three medium potatoes and still feel equally full, even while having consumed 200 extra calories. Carbs and protein have a much greater effect on satiety, and can rarely lead to weight gain when low to no fat sources of protein and carbs are overconsumed.

Because fat is so easily absorbed and utilized in the body, it has the lowest thermic effect of all macro-nutrients and would generate the least heat in itself, however, it still plays a role with uncoupling.

Uncoupling is when protons are transported by ATP synthase into the mitochondrial membrane and ATP is produced as a result. These protons can also leak across the inner membrane by way of uncoupling proteins (UCPs). In this “uncoupled respiration”, energy substrate oxidation and oxygen consumption occur, but the process does not yield ATP. Proton leak is a significant contributor to energy expenditure, accounting for roughly 20-30% of BMR in rats (3). That is why the drug DNP works so effectively for fat burning, because it works via increasing uncoupling, and energy expenditure. However, DNP is pretty dangerous and quite a few people have lost their lives abusing it.

A caloric deficit will reduce the activity of these uncoupling proteins, and can decrease energy expenditure. High-fat diet feeding (in rats) is shown to elevate skeletal muscle uncoupling protein 3 levels but not its activity. (4) Meaning, the elevated UCP3 protein levels did not correlate with proton permeability, or with 24-hour energy expenditure. Instead of increasing dietary fat for more UCP activity, other factors are also able to increase uncoupling, such as cold exposure and total daily calories. Fasting reduces UCP mRNA (which reduces its expression) and refeeding increases it, resulting in diet induced thermogenesis. (5)

So the moral of the story is that total daily calories, and the ability of your mitochondria to produce energy efficiently, is much more important than increasing fat intake for more thermogenesis. Through self experimentation I have found that I was actually more cold while being on a ketogenic diet, with very low carbs, than when consuming adequate amounts of carbs to support my metabolism.


Practical application

The more fats you add in your diet, the more fat your body has to deal with before it can start tapping into it’s own resources and as fats are the most calorie dense, it would be logical to cut them out first.

When picking a fat source for your diet, just be sure to avoid polyunsaturated fatty acids, as they are metabolic inhibitors and inhibit proper thyroid function, increase cortisol, lower androgens, promote obesity, increase inflammation, etc… The list is pretty long, but you get the picture.

When picking your meat source rather choose from chicken breast, top sirloin, silvereye, etc instead of chicken thigh and leg, beef rib-eye, T-bone, etc… and cook your foods only in a little coconut oil, MCT or butter.

I have found that my metabolism and over-all health and well-being is much better when I keep fats on the low side. I’m not talking about trying to eliminate fats completely, but I have seen multiple times that when someone focuses on keeping carbs and protein high and fats moderate to low, that their metabolism speeds up, depending on their carb tolerance.

Everyone is different and responds differently to macro nutrients, so it’s best to start at a certain intake, say 50g of fat daily, and then adjust it from there depending on how you feel.

Aggressive caloric deficits will have a more detrimental effect on your androgens, than when cutting fats too low. Obese men who were in a caloric deficit actually increased their testosterone, however, in healthy lean men it decreased their testosterone. (6)

Studies found that when keeping fat low resulted in a slight drop in testosterone, but it didn’t cause a drop in lean body mass. In direct studies of resistance trained athletes undergoing calorie restricted, high protein diets, low fat interventions that maintained carbohydrate levels appeared to be more effective at preventing LBM (lean body mass) loses than lower carbohydrate, higher fat approaches. These results might indicate that attempting to maintain resistance training performance with a higher carbohydrate intake is more effective for LBM retention than attempting to maintain testosterone levels with a higher fat intake. (7)

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