THE FOSTER STUDY: "A LOW-CARB DIET IS ASSOCIATED WITH FAVORABLE CHANGES IN CARDIOVASCULAR DISEASE RISK FACTORS AT 2 YEARS."
Posted Aug 31 2010 9:59am
You have probably read about the Foster study by now. It has gotten a lot of press coverage and most of the headlines mention that it shows that a low-carb diet is good for the heart. We should all rejoice that that message is (finally!) getting out. The improvements in blood lipid profiles were just too dramatic to be explained away (probably not for lack of trying). But when it comes to weight loss, we hear the same old refrain, "no difference in low fat verses low carb…all diets are the same." I'd like to make a few points about the study that I haven't seen mentioned in other reviews.
1. Here's what the researchers foundIn the first 6 months of the study, the low carbers experienced a greater rise in good cholesterol, lower triglycerides, a greater reduction in blood pressure, a greater reduction in very-low-density liproprotein (VLDL, the bad form of LDL), but less reduction in the large, fluffy, harmless form of LDL. They also lost more weight. It is also noteworthy that they did not suffer bone loss in the study, another mythical danger of such a diet. But after 2 years, the weight loss was about the same for both diets. A closer look reveals a probable explanations.
The participants ate 20 grams of carbs per day for the first 3 months, then they increased the carbs every week by 5 grams per day. They could have been eating 80 grams of carbs per day at the 6 month point. The upper limit for most people to stay in ketosis is 50 grams per day, so for the remaining year and a half of the study, they were probably no longer on a ketogenic (fat burning) diet.
"After 3 months, participants in the low-carbohydrate diet group increased their carbohydrate intake (5 g/d per wk) until a stable and desired weight was achieved."
Do you see the significant word? "Desired." In comparing the weight loss in the two diets, it is important to note that the participants eating the low-carb diet chose how much weight they wanted to lose. The charts that are included in the actual study show their weight loss was greater until the carbs were significantly, and apparently, voluntarily, increased. By the end of the 2 years, those in the low-carb faction may have increased their carb intake so much that what they were eating would hardly qualify as low-carb, although it was probably still lower than those who had to limit fat and calories. So to say the diets were equally effective for weight loss is misleading. Those on low-carb may have reached a preset weight-loss goal or perhaps they just decided to tolerate a few extra pounds in order to go back to eating "normal" food. Whatever their reasons, they decided to eat more carbs and stop their weight loss at some point in the experiment and this is reflected in the graphs included with the report.
2. The researchers state that they did not include anyone who suffered from dyslipidemia (a disruption of blood-fat profile) or diabetes in the study. Both these conditions are symptoms of carbohydrate intolerance. Since approximately 2/3 of the population falls into that category, that means the ones who would have benefited most from carb restriction were excluded. The low-fat dieters in the study were not yet carbohydrate intolerant, but could still be on the road to becoming so in the future if they continue to follow the same diet.
3. Dr. Foster emphasizes the negatives of the low-carb diet, but doesn't mention the great big one associated with the low-fat/low calorie one, which is constant hunger. The low-fat dieters had to limit the total amount of food they ate to 1200 to 1800 calories a day. The low-carb dieters limited the starch and sugar but could eat as much as they wanted from the other food groups. Most people find it difficult to stick to a way of eating that keeps them hungry. He also fails to mention that the complaints were probably limited to the early stages when carbs were severely restricted. A typical high-carb diet causes the body to retain water (that's why high blood pressure is rampant). When the sugar is purged, water goes with it and an ion imbalance may result as minerals are lost along with the water. For most people this causes side effects that will quickly disappear after their bodies have adjusted to the new lifestyle or when the carb count is increased a little. (Switching from a low-carb diet to a low-fat diet also causes side effects.)
Dr. Foster also failed to mention that there are easy solutions for all these complaints. The authors of The New Atkins for a New You say that most of the side effects in the early phase of carb restriction, such as headaches, dizziness, fatigue, bloating, and constipation, can be remedied by drinking more water and getting at least ½ teaspoon of salt per day. The other complaint, bad breath, is simply the result of being in ketosis. (This is also the cause of morning breath—everyone goes into ketosis after an overnight fast.) Some describe it as "fruity" or "sickly sweet," rather than "bad." It is proof that the diet is working and you are burning fat. The remedy is the same as for the other gripes: dilute the ketones by drinking more water.