Saturday, August 16, 2014

Sex-Differences in Cravings After Std. Meals W/ Different Macro Composition - Low Carb + Energy Meals and / or High Amounts Of Fats May Make Female Sugar Cravings Worse

When it comes to carvings, women are more susceptible to the sugar coating of a doughnut vs. steak in a salt crust.
When I saw the results of a recent study from the University of Tokushima Graduate School, I felt reminded of my last barbecue with a couple of friends and how I would have preferred another steak, when my female friends devoured the chocolate cream grimacing as if they were about to have an orgasm.

You're asking yourselves what this anecdote could possibly have to do with the latest nutrition research from Japan? Well, it confirms the main findings Zhou et al. present in their latest paper in the peer-reviewed journal Public Health Nutrition (Zhou. 2014): Men have a significantly stronger desires for salty and fatty foods, whereas women prefer sweet food after meals.
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Before we get into further details (e.g. the fact that the sweetness desire in women was stimulated by increasing fat content of the meal), let's briefly take a look at the study design, first -- The subjects were 130 residents of the Tukushima area who were assigned to two age- and BMI-matched groups according to their sex.
A randomized crossover design was used to investigate each test meal at lunchtime with a 1-week interval between testing sessions. Participants were asked to refrain from skipping meals, to refrain from drinking excessive alcohol and to maintain exercise at a consistent level before each scheduled session. During the study period, participants were randomly assigned into four groups for meals distribution. Group A and group B were administered meals following the sequence of lower to higher ED, and group C and group D were administered meals in the opposite manner. A packed test lunch was systematically provided on aspecified day for six consecutive weeks (Table 1)."
The study was designed such that the majority of daily food and energy consumed was from the test foods, according to the 2010 Dietary Reference Intakes for Japanese.
The male vs. female difference and the female sweet tooth are not completely new: Previous studies have already suggested that men are easy to satisfy with salty foods (Rolls. 1981 & 83). Havel et al. on the other hand were able to show that high fat meals reduce the 24h leptin concentration in women (Havel. 1999) and will - at a molecular level - increase the risk for sweet cravings (Ninomiya. 2001) - an energy dense high(er) carbohydrate meal has after all been shown to bring leptin levels back up (Romon. 1990). No wonder Drewnoski et al. found that obese US women tended to list predominantly sweet foods, such as doughnuts, cookies and cake, while obese men list mainly protein/fat sources (meat dishes) among their favorite foods (Drewnowski. 1992)
Six types of packed lunches were used as test meals with their basic composition and appearance remaining constant (see Table 2). As you would expect from any "truly" Asian diet, rice was the staple food, and the main dishes were sautéed beef, steamed shiitake mushrooms with mincedfish and mixed Japanese hotchpotch consisting of sweet potato, carrot, radish, dried shiitake mushrooms, bamboo shoot, lotus root and konjac.
Table 1: Randomized crossover study design of six different types of test meals* in six experimental sessions (Zhou. 2014)
A green vegetable and kelp seaweed salad as well as tomato and broccoli jelly were also served as an integral part of each meal. The test meals were varied by adding oil or by varying the volume of ingredients and the amounts (80 g or 240 g) of raw vegetable, which were consumed after cooking. The six meals were provided on each test day with varied energy and energy density (ED) as follows:
  1. control meal (Control), energy 500 kcal and ED 0·8 kcal/g; 
  2. high-meat/low-rice meal (Hmeat), energy 513 kcal and ED 0·7 kcal/g; 
  3. low-vegetable meal (Lveg), energy 427 kcal and ED 1·0 kcal/g;
  4. medium-fat/low-vegetable meal (MfatLveg), energy 520 kcal and ED 1·2 kcal/g); 
  5. high-fat meal (Hfat), energy 896 kcal  and ED 1·3 kcal/g; and 
  6. high-fat/low-vegetable meal (HfatLveg), energy 824 kcal and ED 71·8kcal/g
As you can see, the six meals, which differed in vegetable amounts and energy content, were primarily divided into two versions: (i) high-vegetable-content meals contained 240 g of vegetables, which included Control, Hmeat and Hfat meals; and (ii) low-vegetable-content meals contained 80 g of vegetables, which included Lveg, MfatLveg and HfatLveg meals. 
Table 2: Energy and macronutrient composition of the test meals (Zhou. 2014)
The Control, Hmeat and MfatLveg meals had low energy content with approximately 2092 kJ (500 kcal) but different nutritional composition in terms of the protein:fat: carbohydrate ratio.

Alright, let's finally get to the results - Women like sweets and low rice (carbohydrate) and high fat intake make them irresistible, no matter how much veggies they eat

The main study outcomes were the appetite for fullness, satisfaction and prospective demand, and palatability desire for savoury, sweet, salty and fatty foods ratings, the subjects rated after the individual test meals on a 100 mm visual analogue scale (VAS).
"For example, fullness and satisfaction were rated on the 100-mm lines preceded by the questions: ‘How full do you feel right now?’ and ‘How much satisfaction do you feel right now?’, and anchored on the left by ‘not at all’ andontherightby ‘very much’, respectively." (Zhou. 2014)
All participants had been familiarized with the procedure before the first tests were run. We can thus expect that they were able to accurately report their desire for sweet, salty and fatty after consuming the test meals.
Figure 1: Sweet, salty and fatty desire after test meals in men (top) and women (bottom; Zhou. 2014)
If you compare the "sweet desire" of men and women after the test meals, you will realize that the sweet desire of the female subjects was  - independent of the meals macronutrient composition - approximately 25% higher than that of their male peers.

Women are hedonic eaters and into both fat (for flavor) and sweet 

Compared to the men, the women were also much more susceptible to the palatability increase due to increased fat content (compare the graphs on the left to those on the right hand side, Figure 2).
Figure 2: Fullness and satisfaction after test meals in men (left) and women (right; Zhou. 2014).
An increase in fullness, on the other hand, was not achieved by increasing the fat content. And if you go back to the post-meal sweet desire, a high fat content (red dots) did not necessarily reduce the female desire for a sweet dessert, either. In fact, when the meal was changed to the Hfat meal with an
increased fat content by adding oil, sweetness desire was higher in women than in men from 4 h after the meal. The scientists interpret these findings as follows:
Previous studies show: The often-cited increased satiety effects of high fat meals does not exist in women. In response to high fat breakfast and lunch condition (75% fat in the hyperlipidemic vs. 75 % carbohydrate in the hyperglycemic) the 14 young women who participated in a 2003 study by Monteleone did not feel more satiated than they did after the isocaloric (=identical energy content) 75% carbohydrate (closed circles) condition - on the contrary (Monteleone. 2003)!
"Fat, as an important factor increasing palatability in a meal, enhances sensitivity to satisfaction signals by elevating leptin and insulin signalling in the central nervous system (Riedy. 1995; Williams. 2006) .The pleasurable aspects of fat consumption provide a hedonic preference for food due to the rewarding and reinforcing properties of some dietary fats (Drewnowski. 1997; Figlewicz. 2009).

The current study reflects that fat might suppress sweetness desire in a diet with vegetable content as low as 80 g, whereas in a diet with sufficient vegetable content such as 240 g, increased fat content might stimulate the redundant sweetness desire. This stimulation is probably due to initiating a vicious cycle from the increased palatability of the diet. A previous study reported that the increased fat content that promotes the sensory properties of the diet causes insulin/leptin resistance, resulting in more food consumption." (Zhou. 2014)
In other words: The high fat content annuls the beneficial effect of high vegetable intakes - at least in women. Who tend to have a higher tendency for sweet cravings, anyway - a tendency that was strengthened by high fat intakes and triggered and amplified by reduced rice intake as it was the case in the high meat + low energy diet in the study at hand.
Veggies work: One of the most important, yet by no means novel results of the study is that increasing vegetable intake in a diet is effective to enhance fullness and satisfaction regardless of gender. This is thus independent of the increased sweet desire in women with high fat + high vegetable intake.
Bottom line: Is it really just coincidence that the high meat, low energy low carb diet, that triggered the most significant carb cravings is exactly the diet those women are following who email me complaining about being unable to control their cravings - particularly their cravings for sweets? I don't think so and the scientist who highlight in their conclusion that "sweetness desire, especially for women, is also stimulated by decreasing rice [from 150 g to 100g | -33%] intake in the low-ED diet model" (Zhou. 2014) would certainly agree; and that in spite of the fact that they rightly point out that due to the restriction to just one single staple food (rice) the study would have to be repeated with "a Western diet model with bread as the staple food" to find out whether the results may be different | Comment on Facebook!
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