High Protein Diet Induces Sustained Reduction in Ad Libitum Intake Despite Diurnal Leptin Compensation

I've written several hundred posts on this blog.  There are some, especially from early on in 2010, that I would really like my readers to see, and I sure don't expect folks who are just finding this blog now to go back and read everything to find some that I feel are key.  I refer to this study quite often because I think for those finding themselves gaining a little bit each year and not wanting to hop on some "diet rollercoaster", there is merit to -- especially for us women -- upping the protein as a percentage in the diet.  So when I was compiling graphics for the 24 Hour Leptin Profiles post, this study was the first I knew to go to for a graphic.  So, I'm bumping the original, adding a little emphasis to the text but not changing it, and I'll add some commentary on leptin at the end.  

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Original Publish Date:  4/30/10

A high-protein diet induces sustained reductions in appetite, ad libitum caloric intake, and body weight despite compensatory changes in diurnal plasma leptin and ghrelin concentrations

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Dr. Eades on Starvation Diets

When the recent news broke that a Crash Diet (600 cal/day) cured diabetes, discussed HERE,  HERE,  HERE, there was the inevitable invoking of the Minnesota Starvation Experiment in the low carb circles.   A while back, I addressed the MSE in a post entitled Starvation Diets shortly after I had blogged on a study in which one part involved putting three obese women on a 1500 cal/day liquid reducing diet.

The point of that last blog post was that  in the 1970's, the average intake of American women was 1550 cals.   Now folks, keep in mind that averages mean that some women ate less and some ate more.   Dr. Michael Dansinger -- he of the famous diet comparison study and consultant on The Biggest Loser -- told Jimmy during his interview with him that they generally cut the contestants' intake in half on that show.  I don't have time to go back and listen, and the exact numbers aren't really all that important, but the women generally start out eating around 3000 cal/day, so their reducing diet is 1500 cal/day.  Lots of low carbers sneer at TBL as, of course, being the wrong way to lose weight, they could just go low carb and achieve the same results by eating more.  

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Protein & Satiety I

A few studies and such on protein and satiety:

Weight, Protein, Fat, and Timing of Preloads Affect Food Intake

Two foods, one rich in protein (HP) and one rich in fat (HF), were employed to evaluate the effect of macronutrients on food intake and to underline the differences that occurred when the foods were served as uniform meal, as first course of a varied meal, and as a snack 2 h before a varied meal. Our results showed that HP food always exerted a higher effect on both intrameal satiation and postingestive satiety than HF food. When a uniform meal was consumed, satiation for the specific food was reached before fullness; in this condition, sensory characteristics of foods played an important role in controlling food intake and made the uniform meal more satiating than the varied one. The consumption of a snack far from a meal did not contribute to satiety; consequently, gastric filling seems to be an important factor determining the amount consumed in a varied meal.

Add this to my list of articles I have to get a hold of the full text of. 

The influence of thermic effect of food on satiety.

OBJECTIVES: To evaluate energy expenditure after three isoenergetic meals of different nutrient composition and to establish the relationship between the thermic effect of food (TEF), subsequent energy intake from a test meal and satiety sensations related to consumption.

DESIGN: The study employed a repeated measures design. Ten subjects received, in a randomized order, three meals of 2331+/-36 kJ (557+/-9 kcal). About 68% of energy from protein in the high protein meal (HP), 69% from carbohydrate in the high carbohydrate meal (HC) and 70% from fat in the high fat meal (HF).

SETTING: The experiments were performed at the University of Milan. Subjects: Ten normal body-weight healthy women.

METHODS: Energy expenditure was measured by indirect calorimetric measurements, using an open-circuit ventilated-hood system; intake was assessed 7h later by weighing the food consumed from a test meal and satiety sensations were rated by means of a satiety rating questionnaire.

RESULTS: TEF was 261+/-59, 92+/-67 and 97+/-71 kJ over 7 h after the HP, HC and HF meals, respectively. The HP meal was the most thermogenic (P < 0.001) and it determined the highest sensation of fullness (P=0.002). There were no differences in the sensations and thermic effect between fat and carbohydrate meals. A significant relationship linked TEF to fullness sensation (r=0.41, P=0.025). Energy intake from the test meal was comparable after HP, HC and HF meals.

CONCLUSIONS: Our results suggest that TEF contributes to the satiating power of foods.

Breakfasts high in protein, fat or carbohydrate: effect on within-day appetite and energy balance.

OBJECTIVE: To compare the effect of isoenergetically-dense, high-protein (HP), high-fat (HF) or high-carbohydrate (HC) breakfasts (at 08.30) on subjective hunger, fullness and appetite (measured hourly on a 100 mm visual analogue scale), macronutrient balance and ad libitum energy intake (EI), at a test meal (13.30) and throughout the rest of the day (until 23.00).

DESIGN: Six men each spent 24 h in a whole-body indirect calorimeter on three separate occasions during which they received breakfasts designed to match 75% of BMR and that comprised, on average 3.1 MJ of protein (HP), carbohydrate (HC) or fat (HF), respectively, the remainder being split between the other two macronutrients. Every item of the ad libitum diet comprised 13% protein, 40% fat and 47% carbohydrate by energy, with an energy density of 550 kJ/100 g.

RESULTS: Subjectively-rated pleasantness did not differ between the breakfasts, or any of the subsequent ad libitum meals. Subjective hunger was significantly greater during the hours between breakfast and lunch after the HF (26) treatment relative to the HP (18) or HC (18 mm) meals (P < 0.001), although the HP treatment suppressed hunger to a greater extent than the other two treatments over 24 h. However, mean ad libitum lunch intakes were similar at 5.38, 5.30 and 5.18 MJ (NS) on the HP, HC and HF treatments, respectively. After-lunch intakes were also very similar at 6.14, 6.18 and 5.83 MJ (NS). Mean 24-h energy expenditure amounted to 11.12, 11.14 and 10.93 MJ, respectively, producing energy balances of 5.71, 5.83 and 5.04 MJ (NS), respectively. The HP, HF and HC breakfasts led to enhanced P, F and C oxidation, respectively (P < 0.003).

CONCLUSIONS: Large HP, HC or HF breakfasts led to detectable changes in hunger that were not of sufficient magnitude to influence lunch-time intake 5 h later, or EI for the rest of the day. A single positive balance of each macronutrient can be buffered by oxidation and storage capacity, without leading to changes in meal-to-meal EI, when subjects feed ad libitum on unfamiliar diets of fixed composition.

Interesting indeed.  Hunger INCREASED after HF vs. HC or HP (the scores of which seem similar).  But not enough to influence intake.  Still, this flies in the face of the Low Carbventional Wisdom.