Two Days A Week High Protein, Low Carb Fast Cuts >10% of Body Fat in 4 Months And Improves Insulin and Leptin Sensitivity More Than Chronic -25% Energy Restriction

I wonder if she just found out that sheddin 10% body fat can be as easy as doing two "protein modified fasts" per week!?

It has been some time since the last interesting study on Intermittent Fasting has found its way into the SuppVersity news; and I have to admit that the protocol of the study I am about to discuss today does not really qualify as "intermittent fasting" in the "lean gains" sense.

Still, the latest study from the University Hospital of South Manchester NHS Foundation Trust comes with a couple of very interesting results... the only downside is that the subjects were "the usual" ones, namely obese sick people:  115 women with a family history of breast cancer (aged 20 and 69 years). This is problematic, because the same fast during which the obese person draws on his or her fat stores to "survive" can sent the lean sub 10% body fat athlete into a catabolic low energy state and have his blood sugar drop to hypoglycemic levels, when he or she returns to eating ad libitum after the 2 fasting days.

Will intermittent fasting shrink your bust?

Sorry, I just could not resist to use focus on this question of paramount importance. Why? Well the study at hand is the first to actually investigate the negative effects of fasting on your cup size ;-) All jokes aside, this is obviously not a non-sense or cosmetic measure.

As I already mentioned in the introduction, the subjects had a history of breast cancer and in view of the association between breast cancer risk and bra cup size in US women aged <42 (Swanson. 1996) -

• 26% increased risk for cup size B
• 23% increased risk for cup size C
• 95% increased risk for cup size D*

- it does appear to make at least some sense to measure the effect the diet had on bust size, as well (* note: the data was calculated for normal weight women).

Figure 1: Change in body composition in response to dietary energy restriction (-25%; DER) and 2-day per week fasting with calorie (IFC) and carbohydrate (IFCA) restriction on the two fasting days (Harvie. 2013)

So, if you are concerned about losing fat in the wrong places (don't that it may decrease your breast cancer risk to shed superfluous fat on your chest, ladies) the data in figure 1 will probably comfort you. It does after all confirm that the additional loss of abdominal fat (as evidenced by the reduction in waist circumference) is more pronounced than the additional 1-2% reduction in bust size the women in the two intermittent fasting groups, IFC and IFCA experienced.

Details on the protocol:  Diet composition

Side effects? What is interesting and something I have not seen before in a study is an evaluation of differences in side effects and nutrient sufficiency:

• feeling cold (3% DER)
• decreased energy (5% IFC & DER)
• constipation (8% IFC, 3% DER)
• headaches (5% IFC, 3% IFCA)
• bad breath (5% IFC, 3% IFCA)
• light-headed (3% IFC)
• lack of concentration (3% DER)
• mood swings (3% IFC & DER)
• thinking about food 24/7 (8% IFC, 3% IFCA & DER)

Interestingly the different pre-occupation with food did not impact the hunger scores. The only thing the scientists observed was a minimal difference in hunger scores on fasting day 1 in the IFC vs. IFCA group.

Of the usual low-carb diet deficiencies in Mg, Fe, Zn, Ca, vitamins A and D and fibre, the multi compensated everything but the scarcity of magnesium (Mg), zinc (Zn) and selenium (Se) in the IFC group.

The dietary energy restriction (DER) and the intermittent fasting carbohydrate restricted (IFC) groups were isocaloric and contained only 75% of the calculated energy requirements of the women. Contrary to the women in the DER group who consumed a diet with a macronutrient ratio of 25/45/30% protein / carb / fat, the subjects in the IFC group were however

"asked to restrict energy and carbohydrate on two consecutive days each week (70 % energy restriction and 40 g carbohydrate) and to consume a euenergetic Mediterranean-type diet that met their estimated energy requirements for the remaining 5 d of the week."

The restricted IFC diet the subjects consumed on those "fasting days" provided between 625kcal/day and 680kcal/day and included approximately

• 250 g of protein foods including lean meat, fish, eggs, tofu, textured vegetable protein, 
• three servings of low-fat dairy foods (e.g. 195 ml semi skimmed milk, 150 g low-fat yoghurt, 30 g low-fat cheese), 
• four portions of low-carbohydrate vegetables and 
• one portion of low-carbohydrate fruit, 
• at least 1170 ml of other low-energy fluids, and 
• an over-the-counter multivitamin and mineral supplement providing the RDA for vitamins and typically 20 – 50 % for minerals on restricted days.

Lastly, the subjects in the IFCA protocol followed the exact same rulez, but were allowed to consume "unlimited lean meat, fish, eggs, tofu, MUFA and PUFA on restricted days." In addition, the saturated fat content of both intermittent diets was limited to 10% and alcohol consumption was discouraged, but not prohibited.

Addendum: In view of the fact that the question arose several times both here in the comments and on facebook, I want to point out that the 250g of protein foods are not identical to 250g of protein. They will rather contribute max. 50-90g of protein and will thus not go beyond the dietary constraints of 625kcal. Apropos, other than one commenter suspected the weekly caloric deficit was indeed identical in the DER and the IFC group. Let's to the math with simplified figures: Baseline intake 2,000kcal - 25% => 7x400kcal = 2,800kcal deficit in the DER group vs. 2x (2000kcal-600kcal) = 2,800kcal on the two consecutive low carb fasting days in the IFC group.

"And what about the 'health effects'?"

It we take a look at the serum markers, it's actually quite surprising that there were no significant improvements in HbA1c, blood glucose, IL-6, TNF-alpha, adiponectin, cholesterol and triglycerides. After all, this is what we almost expect with any type of fat loss.

Figure 2: Changes in blood glucose and insulin resistance, as well as leptin levels after 3 month on the respective diets and another month on "weight maintenance" when 68% of the ICF & ICFA subjects stuck to their protocol (Harvie. 2013)

The comparatively high fat loss in the IFC and ICFA groups (-12% and -11% over the three months of dieting) did yet result in significant improvement in insulin sensitivity and had a much more pronounced effect on the leptin levels, which is - in the case of overweight individuals - a good thing, as it signifies a reduction in "leptin resistance".

Altough they were allowed to, the IFCA subjects (middle bar) did not eat much more protein and fat than their peers in the IFC group.

Bottom line: Overall the results of the study at hand leave no doubt that a carbohydrate restricted 5:2 day (5 days you eat normal, 2 days you fast) high protein fasting strategy is a very effective means to shed body fat and increase your insulin sensitivity - for the overweight individual (!).

In that, it's worth mentioning that you do not even have to force yourself to abstain from foods altogether on the two fasting days: It's actually sufficient to cut the carbs by 43 % (which was the effective reduction in the IFC & IFCA groups compared with 23 % for the DER group) as long as you are not into fatty foods and don't compensate for that by overconsuming protein and fats... yep, you heard me right, there is NO MAGIC in low carb dieting that would allow you to eat as much protein and fat as you want and still lose weight. The subjects in the IFCA who were allowed to do so added no more than 10g of extra protein and 15g of fat to your ~600kcal allowance on the fasting days.

Now, I am not sure how realistic it is that everyone will do the same as the subjects in the IFCA group and refrain from overeating on eggs, sausages of even Quest protein bars and all the other delicious(ly convenient) ready made "low carb foods" that are flooding the market these days. If you are a trainer or nutritionist, I would thus suggest you don't tell them they allowed to eat "as much as they want as long as it contains no carbs" ;-)

References: 

• Harvie M, Wright C, Pegington M, McMullan D, Mitchell E, Martin B, Cutler RG, Evans G, Whiteside S, Maudsley S, Camandola S, Wang R, Carlson OD, Egan JM, Mattson MP, Howell A. The effect of intermittent energy and carbohydrate restriction v. daily energy restriction on weight loss and metabolic disease risk markers in overweight women. Br J Nutr. 2013 Apr 16:1-14. [Epub ahead of print]
• Swanson CA, Coates RJ, Schoenberg JB, Malone KE, Gammon MD, Stanford JL, Shorr IJ, Potischman NA, Brinton LA. Body size and breast cancer risk among women under age 45 years. Am J Epidemiol. 1996 Apr 1;143(7):698-706.