More Protein, Less Refined Starch Important for Dieting, Large Study Shows
ScienceDaily (Nov. 26, 2010)
— Researchers at the Faculty of Life Sciences (LIFE), University of
Copenhagen, can now unveil the results of the world’s largest diet
study: If you want to lose weight, you should maintain a diet that is
high in proteins with more lean meat, low-fat dairy products and beans
and fewer finely refined starch calories such as white bread and white
rice. With this diet, most people can also eat until they are full
without counting calories and without gaining weight.
Finally, the extensive study concludes that the official dietary recommendations are not sufficient for preventing obesity.
The large-scale random study called Diogenes has investigated the
optimum diet composition for preventing and treating obesity. The
results were recently published in the New England Journal of Medicine.
The objective of the Diogenes study has been to compare the official
dietary recommendations in Europe, including the Danish
recommendations, with a diet based on the latest knowledge about the
importance of proteins and carbohydrates for appetite regulation. A
total of 772 European families participated, comprising 938 adult
family members and 827 children. The overweight adults initially
followed an 800 kcal/day diet for eight weeks, losing an average of 11
kg. They were then randomly assigned to one of five different low-fat
diet types which they followed for six months in order to test which
diet was most effective at preventing weight regain. Throughout the
project, the families received expert guidance from dieticians and were
asked to provide blood and urine samples.
The five diet types
The design comprised the following five diet types:
- A low-protein diet (13% of energy consumed) with a high glycemic index (GI)*
- A low-protein, low-GI diet
- A high-protein (25% of energy consumed), low-GI diet
- A high-protein, high-GI diet
- A control group which followed the current dietary recommendations without special instructions regarding glycemic index levels
A high-protein, low-GI diet works best
A total of 938 overweight adults with a mean body mass index (BMI)
of 34 kg/sq m were initially placed on an 800-kcal-per-day diet for
eight weeks before the actual diet intervention was initiated. A total
of 773 adult participants completed this initial weight-loss phase and
were then randomly assigned to one of five different diet types, where
548 participants completed the six-month diet intervention (completion
rate of 71%).
Fewer participants in the high-protein, low-GI groups dropped out of
the project than in the low-protein, high-GI group (26.4% and 25.6%,
respectively, vs. 37.4%; P = 0.02 and P = 0.01 for the two comparisons,
respectively). The initial weight loss on the 800-kcal diet was an
average of 11.0 kg.
The average weight regain among all participants was 0.5 kg, but
among the participants who completed the study, those in the
low-protein/high-GI group showed the poorest results with a significant
weight gain of 1.67 kg. The weight regain was 0.93 kg less for
participants on a high-protein diet than for those on a low-protein
diet and 0.95 kg less in the groups on a low-GI diet compared to those
on a high-GI diet.
The children’s study
The results of the children’s study have been published in a
separate article in the American medical journal Pediatrics. In the
families, there were 827 children who only participated in the diet
intervention. Thus, they were never required to go on a diet or count
calories — they simply followed the same diet as their parents.
Approx. 45% of the children in these families were overweight. The
results of the children’s study were remarkable: In the group of
children who maintained a high-protein, low-GI diet the prevalence of
overweight dropped spontaneously from approx. 46% to 39% — a decrease
of approx. 15%.
Proteins and low-GI foods ad libitum — the way ahead
The Diogenes study shows that the current dietary recommendations
are not optimal for preventing weight gain among overweight people. A
diet consisting of a slightly higher protein content and low-GI foods
ad libitum appears to be easier to observe and has been documented to
ensure that overweight people who have lost weight maintain their
weight loss. Furthermore, the diet results in a spontaneous drop in the
prevalence of overweight among their children.
About glycemic index
The glycemic index is a measure of the ability of carbohydrates to
increase blood glucose levels when absorbed in the body. Food with a
low-glycemic index (LGI) causes blood glucose levels to increase more
slowly and to lower levels compared to high-carbohydrate foods with a
high glycemic index
Drastic increases in blood glucose levels give rise to several
potentially undesirable effects that can influence the body’s
metabolism as well as our ability to perform mentally. It is therefore
most appropriate to maintain a diet that results in slow digestion and
thus more stable blood glucose levels and greater satiety.
A diet with a high protein content contains many protein-rich foods
such as lean meat, poultry, fish, eggs and low-fat dairy products.
Legumes also contain high levels of protein, as do nuts and almonds.
Proteins are significantly more filling than both carbohydrates and fat.
Special requirements for a low-glycemic diet
The glycemic index applies to carbohydrate-containing foods. The
recommendations are that some types of fruit may be consumed ad
libitum, such as apples, pears, oranges, raspberries and strawberries.
Other types should be eaten in only very limited amounts, including
bananas (especially overripe bananas), grapes, kiwi, pineapple and
melon. Nearly all vegetables are permitted, with the exception of corn,
which should be limited. Carrots, beets and parsnip should preferably
be eaten raw.
With regard to cereal-based foods (bread, grain, corn, hulled grains
and breakfast products), the goal is to eat as many coarse and
wholegrain foods as possible, i.e. wholegrain breads with many kernels,
wholegrain pasta, whole oats and the special varieties of wholegrain
Potatoes should be cooked as little as possible. Try to stick to new
potatoes, and it is a good idea to eat them cold. Avoid mashed potatoes
and baked potatoes.
Pasta should be cooked al dente and is best eaten cold.
Choose rice varieties such as brown rice, parboiled rice or basmati.
White bread without kernels, white rice and sugary breakfast
products should be avoided. In general, sugar intake should be limited,
not so much because of its GI but to avoid all those ’empty calories’.
Recommended GI values:
Over 70 — high GI 55-70 — medium GI Under 55 — low GI
High-GI foods can still be healthy and vice versa. Carrots, for
instance, have a high GI (72), while chocolate has a low GI (49). Fats
help decrease the absorption of sugar in the blood, which means that
carbohydrate-containing foods and fat can have a low GI.
Example of a day’s menu for a high-protein, low-GI diet
If you want to maintain a high-protein, low-GI diet, daily meals could be composed as follows:
Breakfast: Low-fat A38 yogurt with muesli (without added sugar), wholegrain crispbread with low-fat cheese, an orange
Morning: Vegetable sticks and low-fat cheese sticks
Lunch: Wholegrain rye bread with lean meat or chicken cold cuts, mackerel in tomato sauce and misc. vegetables
Afternoon: Wholegrain rye bread with low-fat liver pâté and cucumber
Dinner: Stir-fried turkey with vegetables and wholegrain pasta; avocado salad with feta cheese and sugar peas
It is best to drink water or low-fat milk with meals.
To sum up, there is nothing particular about this diet with the
exception of the above-mentioned limitations, special cooking
instructions and the fact that certain vegetables should be eaten raw.
This diet generally complies with the official dietary recommendations
of eating plenty of fruit and vegetables, low-fat foods, plenty of
fibre and limiting sugar intake.