|High fat + high carbohydrate foods like mini doughnuts are exactly what you should not eat on a refeed day, let alone during weeks of bulking.|
Yes? In this case, I would suggest you take a closer look at the following overview of the research. An overview that is probably not complete, but it should suffice to provide preliminary answers to the aforementioned questions.
- The amount of weight you gain depends on your genes: They are not the only determinant. That's for sure. A 1990 study by Bouchard et al. still leaves no doubt that your genes are one of the most important determinants of the quantity of weight you gain.
In said study the researchers from the Laval University fed 24 sedentary young male twins 1,000kcal extra for six out of seven days of the week. In that the study is not the first to investigate the effects of overfeeding on weight gain in twins. It is yet the first and only one that did this over a period of 100 days and thus with a total energy excess of 84,000 kcal on a diet that contained 50 percent carbohydrate, 35 percent fat, and 15 percent protein.
According to Ukkola, et al. (2001), the genetic differences may partly be mediated by differences in the genetic make-up of ones beta-2 adrenoreceptors with specific variants being associated with greater increases in insulin resistance, body weight and subcutaneous fatness. Other candidates are the cholesterol ester transfer protein (CETP) gene which appears to affect adiposity in response to long-term overfeeding (Terán-García. 2008). Other scientists use similar genetic polymorphisms to explain a general resistance to weight gain during overfeeding via genetically determined variations in nonexercise activity thermogenesis (Vanltallie. 2001).
- Overfeeding fat, carbohydrate or protein, does it make a difference? Studies that compare isocaloric overfeeding are quasi non-existent. What we do have are studies like the one by Horton et al. (1995) that compared high fat vs. high carbohydrate diets (see Figure 2 for macronutrient composition), where the additional energy came from fat or carbohydrates.
In the Horton study this was a 50% extra that was added in form of fat or carbohydrates on top of the baseline diets of the normal-weight and obese subjects. A 50% extra that lead to significant weight gain.
Figure 3: Weight gain (left) and increase in energy expenditure (right) in obese and lean subjects in response to carbohydrate and fat overfeeding (Horton. 1995).
No! Carbs are not necessarily more fattening in the obese. It's a commonly held prejudice that carbohydrates are more readily coverted to fat and stored in the obese, but a study by Minehira et al. that investigated just this found that there was not just no difference in de novo lipogenesis with carbohydrate overfeeding between lean and obese individuals, there was also no increase in de novo lipogenesis, at all, when the when the obese subjects were overfed with a high carbohydrate diet for one day (Minehira. 2004).
Figure 4: Proportion of the energy that was stored as body fat (Horton. 1995).
Last but not least, it may also be worth mentioning that the the fat gain in the obese group was 89% and 57% higher in the carbohydrate and fat overfeeding group, respectively. An intriguing result that appears to stand in line with dieting studies, where high fat diets are superior to high carbohydrate diets in the obese, but not in lean individuals.
What was not different for obese and lean individuals, though, was the the fact that the carbohydrate overfeeding lead to higher gains in lean mass than the fat overfeeding. A result that should remind you of a previously reported study here at the SuppVersity, in which a no fat bulk lead to significantly greater muscle and significantly lower fat gains than a low fat bulk (see "If You Go "High Carb", You Better Go Really High!" | more). Overall, "bulking", i.e. eating more than you need on any mixed diet, has repeatedly been shown to produce significant increases plasma Somatomedin-C/Insulin-like Growth Factor (SM-C/IGF-l) and testosterone concentrations as well as insulin, of which Forbes et al. speculate that they promote the lean mass increases that are particularly pronounced when overfeeding is combined with resistance training.
In a more nutrient-type specific study b by Dirlewanger that did not focus on the weight gain or anabolism, but on the leptin response and the increase in resting energy expenditure the subjects experienced a significant increase in leptin (+28%) and resting energy only in the high carbohydrate, yet not in the fat overfeeding arm of their study in young, lean individuals (Dirlewanger. 2000). Other studies, without clear distinction between high carb and high fat overfeeding, indicate that fast food like burgers or fries is an effective short-term leptin stimulator, too - at least if it's consumed in a single binge (Kolaczynski,. 1996).
Figure 5: Energy partitioning in young men upon overfeeding with ~5,000kcal per day - mostly carbohydrates, i.e. 1% protein, 3% fat, and 86% carbohydrate (Acheson. 1988).
If you consume sugar on a refeed, should you prefer glucose, sucrose of fructose? In view of the fact that I don't suggest you refeed more than 1-2 days and considering the fact that you want to get the majority of your carbs from starches on a true bulks, it does not really matter. In fact, studies show no difference in de novo lipogenesis in 96h overfeeding studies between pure glucose and sucrose, which is a 1:1 combination of fructose or fructose in two studies in lean and obese women by (McDevitt. 2000 & 2001). In the long run, consuming amounts of fructose you could only get by drinking a couple of bottles of coke everyday, will yet not be favorable for your health - even if taking fish oil can blunt the increase in hepatic de novo lipogenesis, it won't blunt the insulin resistance (Faeh. 2005).
Modifications of which Meugnier et al. show that they stimulate the synthesis of triacylglycerol, inhibit lipolysis and reduce the oxidation of fatty acid oxidation, while promoting the development of adipocytes with an excess of only ~550kcal/day from fat per day (see Figure 6).
Another potential explanation is the change in thyroid hormones, of which the data in Figure 7 from an overfeeding study by Danforth Jr., et al. (1979) tells you that the high protein overfeeding despite a 29.8% lower total energy intake triggered the most, the carbohydrate diet the 2nd most favorable (=in favor of greater energy expenditure) effects on the thyroid hormone.
Figure 7: Effects of overfeeding with carbohydrates, fats, and protein on thyroid hormones (Danforth, Jr. 1979). Figure 8: Estimates thermic effect of carbohydrates fats, protein, and alcohol in % energy of the energy that's ingested in form of the respective nutrients (Joosen. 2006).
- Classic overfeeding studies with protein as a single nutrient are yet unfortunately rare. Even less, namely nothing, is known about the effects of ketogenic diets, which is why it's at the moment impossible to tell whether a hypercaloric high fat diet that is devoid of carbs and low enough in protein to actually induce ketosis will have the same negative effects as a high fat diet that still contains 15-30% carbohydrates and some protein.
Based on the studies we have, it's yet quite certain that the combination of some carbs and a high amount of fat is the most obesogenic variety of "bulking" you could possibly select. Therefore - with the exception of ketogenic diets, where corresponding data is still missing, the rule of thumb is: The more fat in the diet, the more rapid the body fat, but not necessarily the body weight gain.
- MCT overfeeding is less obesogenic - The reason that rodents that are overfed with medium-chain triglycerides (Geliebter. 1983) and assumable human beings store less fat than on long-chain triglycerides as you will find them in your bacon, sausages, dairy & co is an increase in thermogenesis that has been observed in both rodent and human studies.
Figure 10: Metabolic rate in healthy men after the ingestion of isocaloric fat meals containing MCTs or long chain triglycerides (Hill. 1989).
Still, in theory it would appear as if using MCTs in a dieting context makes sense. In reality, studies have shown that using MCTs as a major source of your dietary fats does not lead to significant long-term improvements in fat or general weight loss - even if 27% of an 800kcal/day starvation diet were pure MCT oil (Yost. 1989).
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- Antonio, Jose, et al. "The effects of consuming a high protein diet (4.4 g/kg/d) on body composition in resistance-trained individuals." Journal of the International Society of Sports Nutrition 11.1 (2014): 19.
- Bouchard, Claude, et al. "The response to long-term overfeeding in identical twins." New England Journal of Medicine 322.21 (1990): 1477-1482.
- Danforth Jr, E., et al. "Dietary-induced alterations in thyroid hormone metabolism during overnutrition." Journal of Clinical Investigation 64.5 (1979): 1336.
- Dirlewanger, M., et al. "Effects of short-term carbohydrate or fat overfeeding on energy expenditure and plasma leptin concentrations in healthy female subjects." International journal of obesity and related metabolic disorders: journal of the International Association for the Study of Obesity 24.11 (2000): 1413-1418.
- Faeh, David, et al. "Effect of fructose overfeeding and fish oil administration on hepatic de novo lipogenesis and insulin sensitivity in healthy men." Diabetes 54.7 (2005): 1907-1913.
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