Mediterranean Diets: low-carb versus low glycemic load

Spanish Ketogenic Mediterranean diet: a healthy cardiovascular diet for weight loss
Original source: Nutrition Journal 2008, 7:30
Authors: Joaquin Perez-Guisado (corresponding author), Andres Munoz-Serrano, and Angeles Alonso-Moraga
Publication date: 26 October 2008
DOI (digital document ID): 10.1186/1475-2891-7-30
Requires subscription? No
Publicly-available abstract: Yes

Enhancement of a modified Mediterranean-style, low glycemic load diet with specific phytochemicals improves cardiometabolic risk factors in subjects with metabolic syndrome and hypercholesterolemia in a randomized trial
Original source: Nutrition & Metabolism 2008, 5:29
Authors: Robert H Lerman (corresponding author), Deanna M Minich, Gary Darland, Joseph J Lamb, Barbara Schiltz, John G Babish, Jeffrey S Bland, and Matthew L Tripp
Publication date: 4 November 2008
DOI (digital document ID): 10.1186/1743-7075-5-29
Requires subscription? No
Publicly-available abstract: Yes

Synopsis:
Both of these studies looked at variants of the Mediterranean Diet, followed over a period of 12 weeks (three months). The Spanish study emphasized the use of virgin olive oil as the primary source of dietary fat, green vegetables and salads as the primary source of carbohydrates, and fish as a primary source of protein. The US study is a follow-on to a previous study comparing a low-glycemic-load Mediterranean diet with added soy protein and phytosterols (plant-based fats) to the American Heart Association's diet plan. In this study, the diet is supplemented with plant-derived substances (phytochemicals) that they believe will improve insulin sensitivity and reduce cardiovascular and metabolic risk factors.

In the Spanish study, 31 obese people (BMI approximately 36) in their mid- to late-thirties were studied. They were not given caloric limits, but their diets included approximately 2 tablespoons of virgin olive oil (2 teaspoons per meal), 1-2 glasses wine daily (half at lunch and half at dinner),
green vegetables and salads to a maximum of 30 g carbohydrate per day, and unlimited protein. Non-nutritive sweeteners were allowed on this diet. Protein was divided into "fish" and "non-fish" (meat, fowl, eggs, shellfish and cheese), with "fish" and "non-fish" being consumed on separate days, and at least four "fish days" per week. In addition, subjects were allowed up to two cups of coffee or tea per day, and required to drink at least three liters of water per day. The subjects were given a standard multivitamin-and-mineral supplement and a calcium supplement; they were also asked to check their urine for ketones using ketostrips.

• Results: After 12 weeks, the subjects lost about 14 kg (30-35 lb), lowered their blood pressure (by about 15 points (millimeters mercury) systolic and 9 points diastolic), lowered their total cholesterol about 10%, significantly dropped their triglyceride levels (from about 218 down to 114 mg/dl), and reduced their fasting blood glucose level about 16 mg/dl. In addition, LDL ("bad") cholesterol levels dropped about 8%, and raised their HDL ("good") cholesterol about 9%. While the subjects were not heavy enough to have moved from "obese" to "overweight" in this time frame, the measured changes moved the patients' statuses from "prehypertension" to "normal blood pressure", from "prediabetic" to "normal", and from "high cholesterol" to "normal cholesterol". Based on the factors used to diagnose it, these subjects would be considered to no longer have metabolic syndrome. The researchers did not measure the beginning and ending percentages of body fat versus muscle mass, but their visual observation suggests that the weight lost was primarily fatty tissue.
• Limitations: The study had a number of limitations, including small size, short duration, highly-selected population, no measurement of total caloric intake, and the possibility that weight loss alone, as well as any of the factors of the program -- either by itself or in combination with others -- may have accounted for these changes. The authors suggest further study with a larger group of people, for a longer period of time, and also comparison with other low-carb diets.

The US researchers' initial viewpoint is that modern diets induce tissue inflammation, resulting in metabolic syndrome. They state that a number of active ingredients in medicinal plants target the pathways of this inflammation, and believe that the addition of these active agents to a low-glycemic-load adaptation of the Mediterranean diet can assist the body in repairing this damage. The US study included 49 patients with metabolic syndrome, average age 53 years, average BMI approximately 34. All subjects had high LDL cholesterol and triglycerides, and had at least two of the other signs used to diagnose metabolic syndrome (low HDL cholesterol, stage I hypertension or drug-treated hypertension, large waist size, and impaired fasting glucose. Half were put on a modified Mediterranean diet alone; the other half were put on the modified diet with the inclusion of phytochemical supplements. The two groups were split out in a way to minimize the initial differences between them.
In this version of the Mediterranean diet, wine was limited to 1 glass per day. Whole grains were allowed, but only one serving per day. Vegetables were mostly limited to very low glycemic load vegetables, with a maximum of one "occasional" serving of a small category of
phytochemical-rich vegetables with a moderate glycemic index (55-70). The only sweeteners allowed were stevia and low-glycemic agave nectar syrup.
The group receiving phytochemical supplementation received a nutritional supplement beverage (powdered) and supplement tablets. All subjects were required to engage in moderate aerobic exercise (at 70-75% target heart rate) for at least 2.5 hours per week. Food cravings, as well as food intake and satiety levels, were monitored (patient-generated logs and surveys). The results were analyzed, accounting for the effects of weight loss, consuming fewer calories, and consuming lower levels of carbohydrate.

• Results: At the end of 12 weeks, the diet-alone subjects lost about 5.7 kg (about 12.5 lb), and the supplemented group about an extra half-pound. While both groups showed lowered total cholesterol, LDL, and triglycerides, the group receiving the supplements saw greater reductions in these readings. Only the group with the supplements had increased HDL cholesterol. The group receiving the supplements were able to lower both systolic and diastolic blood pressure by about 6 points, while those receiving diet alone were only able to lower their systolic blood pressure, by about 4 points. Hemoglobin A1c (HbA1c), a measure of long-term blood glucose levels, went down in both groups, but fasting blood glucose did not drop in the group receiving supplements. Twice the number of subjects in the group receiving supplements were able to move from "having metabolic syndrome" to "normal".

Reliability:
The authors in the Spanish study are associated with the Genetics department of the University of Cordoba and do not report any conflicts of interest. Their bibliographic references are from peer-reviewed journals, mostly in the realm of nutrition.

The authors in the US study all work for the MetaProteomics, a research subsidiary of Metagenics, a company which produces and sells dietary plans, including a number of dietary supplements and meal replacement formulas, which it states will improve the health, weight,
and longevity of people with metabolic syndrome and cardiovascular disease. The MetaProteomics subsidiary is aimed at research into human proteins and how specific chemicals in foods are used by the human body. The bibliographic references are from peer-reviewed journals, and their source research is aimed more at finding the causes of cardiometabolic disease as well as specific chemicals that might lessen the probability of developing these diseases. As employees of a subsidiary of Metagenics, the authors' research is aimed at developing new products (both diets and supplements) for Metagenics to sell.

Both studies are limited in small sample size over short amounts of time; additionally, the Spanish study considers fewer variables.

There are significant differences in the two low-glycemic/low-carb "Mediterranean diets" studied: the Spanish study centers on healthy proteins and fats, while the US study aims more at trying to determine the effect of an anti-inflammatory diet and of the phytochemical
supplements the company sells.

Practical Applications:
Both versions of "Mediterranean diet", unsupplemented, showed favorable changes in cholesterol levels and blood glucose levels. The Spanish study showed greater changes in weight loss, blood pressure, triglycerides, and HDL cholesterol than the US study including supplements; however, the limitations of both studies does not indicate how effective either diet is at maintaining long-term health, or how safe they are over long periods of time.

Any highly-restrictive diet has its limitations, and even some less-restrictive diets may not be suitable for your personal medical conditions. Please consult your doctor and nutritionist before making any large-scale changes to your diet.

This synopsis and comparison was based on the full articles.

Does "dashboard dining" make you fat?

The joint impact on being overweight of self reported behaviours of eating quickly and eating until full : cross sectional survey
Original source: British Medical Journal BMJ 2008;337:a2002
Authors: Koutatsu Maruyama, Shinichi Sato, Tetsuya Ohira, Kenji Maeda, Hiroyuki Noda, Yoshimi Kubota, Setsuko Nishimura, Akihiko Kitamura, Masahiko Kiyama, Takeo Okada, Hironori Imano, Masakazu Nakamura, Yoshinori Ishikawa, Michinori Kurokawa, Satoshi Sasaki, Hiroyasu Iso (corresponding author)
Publication date: 21 October 2008
DOI (digital document ID): 10.1136/bmj.a2002
Requires subscription? No
Publicly-available abstract: Yes

Synopsis:
Researchers in Japan surveyed over 3000 adults for one month, over a period of three years, to see if eating quickly, or eating until one is full, or both, makes people overweight. For the purpose of this research, "overweight" was considered to be having a body mass index (BMI) of greater than 25.
The adults, in one suburban and one rural community in Japan, were asked to rate themselves on how fast or slow they ate and on whether or not they routinely ate until they were full. The self-reporting was confirmed by the subjects' friends.

People with eating disorders such as binge eating disorder, gorging, and anorexia nervosa were excluded from the study, as were people with disordered eating, people with cardiovascular disease, and people who could not tell whether they ate quickly or slowly and/or who could not tell when they'd eaten until full.

The results were adjusted for several variables, including age, caloric intake, physical activity, smoking, and for possible effects of the specific community.
The results were also examined to find out if there was an additive interaction between eating quickly and eating until full (i.e., if one were more likely to be overweight if one both ate quickly and ate until full).

Just over half of the men, and about 58% of the women, said they ate until full. (These people consumed approximately 100 calories more per day, per person than the rest of the population.) Just under half of the men, and over a third of the women, said they ate quickly.

The results suggest that people who eat until full are twice as likely to be overweight as those who walk away from the table slightly hungry; also, that people who eat quickly are twice as likely to be overweight as those who eat slowly. People who eat until full and who eat quickly are over three times as likely to be overweight as those who do not eat quickly, and who leave the table slightly hungry.

The article contains an editorial sidebar that suggests that eating quickly, and/or eating until full, may be contributing factors to overweight and obesity independent of any other eating and exercising behaviors.


Reliability: Despite the large sample size and independent verification, the data were based on self-observation and therefore have the potential of being skewed. On the other hand, many or most of the factors that could give a false reading were accounted for and neutralized. Also, given that people who ate until full consumed 100-150 more calories per day than those who did not, one month may not be sufficient time to draw a theory of causality (that eating rapidly, or eating until full, causes overweight). The article itself does not draw any conclusions as to the reasons for the association between these eating behaviors and overweight, nor does it claim complete independence of factors beyond the ones adjusted for. Given that BMJ appears to posit a direct connection, more stringent research may be needed to test this theory.

Practical Applications: If direct connections can be made between eating quickly, and/or eating until full, and overweight, then it points to the need for education, and possibly abolishing the half-hour-or-shorter meal break, in favor of a longer one.

This synopsis was based on the entire article.