It’s no secret that following a low-carb diet can result in weight loss. The frustrating thing about this low-carb madness is that supporters continually highlight the ‘up-side’ of the diet, with virtually no mention of the consequences.
While weight loss may be exactly what you’re after, the missing piece in this crazy puzzle is the long-term effect that it could be having on your body. In truth, we have no idea what that effect could be!
Factors contributing to weight loss in low-carb diets
- Loss of water weight – carbohydrate stores help maintain fluid levels, therefore if you deplete carbohydrate, water will be lost as a result.
- Decreased appetite – the ketogenic nature of the diet leads to appetite suppression.
- High protein content is highly satiating (feel fuller for longer), and therefore reduces food intake.
- Reduced calories – carbohydrates foods usually provide a very large proportion of a person’s diet, but on a low-carb diet, they are limited, and therefore result in severe calorie reduction. Therefore, it is the restriction of food which causes weight loss, not the restriction of carbohydrates, as many believe.
So, what really happens in the body when you follow a low-carb diet?
- When carbohydrate is digested, glucose is absorbed into the blood stream, the liver stores excess glucose by converting it to glycogen.
- Once the body digests all the carbohydrate from your last meal, the liver begins to convert its stored glycogen back into glucose, to help maintain glucose levels in the blood.
- When the liver runs out of glycogen, it begins a process called gluconeogenesis, to further increase the circulating blood glucose concentration.
- The liver begins breaking down fat into fatty acids and ketone bodies.
- Brain and nerve cells slowly convert over, from being consumers of glucose, to partial consumers of ketone bodies for energy – this is ketosis.
- Eventually the body may begin to break down muscle cells if necessary.
We already know that our bodies preferred source of energy is carbohydrate. If we don’t need carbohydrate, as some state, why would they be the the preferred source?
As we’ve seen, if deprived of adequate carbohydrate, the body’s design is so amazing that it can turn to other sources. This method of survival is an inbuilt mechanism to help us in a starvation situation, it was never intended to be a weight loss mechanism.
Why is carbohydrate essential to our body?
- It provides a steady and easily accessible supply of energy to the body.
- It is the main source of energy for the brain and central nervous system.
- If carbohydrate intake is low, the body may eventually begin to use protein – directing protein away from its intended use could lead to inadequate supplies being available for normal muscle repair.
Possible long-term side effects of a low-carb diet
A study published in the Asia Pacific Journal (2003) indicates some of the possible complications linked to long-term restriction of carbohydrates in the diet:
- Heart arrhythmias
- Cardiac contractile function impairment
- Sudden death
- Kidney damage
- Increased cancer risk
- Impairment of physical activity
- Lipid abnormalities
- Abnormal liver function
What about the scientific evidence?
There are so many studies in this area, many for low-carb eating, and many against! Where to begin is daunting, however I’ve listed a few for consideration.
In favour of low-carb diets:
- A study published in JAMA (2007) found that the women lost significantly more weight (4.7 kg) on the Atkins diet, than on 3 higher-carbohydrate diets (LEARN 2.6 kg, Ornish 2.2 kg, and Zone 1.6 kg), without increasing cardiovascular risks. The authors conclude: “Concerns about adverse metabolic effects of the Atkins diet were not substantiated within the 12-month study period.” This study has however been criticized for being fatally flawed.
- A study published in the Annals of Internal Medicine (2004) found that, “Participants on a low-carbohydrate diet had more favourable overall outcomes at 1 year than did those on a conventional diet. Weight loss was similar between groups, but effects on atherogenic dyslipidemia, and glycaemic control were still more favourable with a low-carbohydrate diet.”
Against low-carb diets:
- A scientific review published in Obesity Research (2001) concluded that low-carb dieters’ initial advantage in weight loss was a result of increased water loss, and that after the initial period, low-carbohydrate diets produce similar fat loss to other diets with similar caloric intake.
- A systematic review of low carbohydrate diets found that weight loss achieved is associated with the duration of the diet, and restriction of energy intake, but not with restriction of carbohydrates.
- A study published in the New England Journal of Medicine found that, “The low-carbohydrate diet produced a greater weight loss (approximately 4%), than did the conventional diet for the first six months, but the differences were not significant at one year. The low-carbohydrate diet was associated with a greater improvement in some risk factors for coronary heart disease.”
- A small study published in the journal Hypertension, found that low-fat diets are more effective in preserving and promoting a healthy cardiovascular system than low-carbohydrate diets.
- A clinical trial published in the American Journal of Clinical Nutrition (2006) found an improvement in insulin function after 6 weeks in both groups studied, with no significant difference in the amount of weight lost in either group. The low-carb group however reported feeling greater emotional discomfort, than the higher-carb group. Moreover, the low-carb group also exhibited higher levels of inflammation in their blood.
Unfortunately, there really is no magic bullet to weight loss. However, high-protein, low-carb diets are definitely not recommended. The restricted nature of such plans, and general lack of variety, confirms to me that this diet could not be recommended in good conscience.
What are your thoughts on this? Are you for, or against, low-carb diets?
Other links you may want to check out:
- The Pitfalls of a Low-Carb Diet – The American Cancer Society says low-carb diets “can be a high-risk option,”
- Telling People What They Want to Believe – Dean Ornish, M.D., examines low-carb diets in Journal of the American Dietetic Association
- American Heart Association statement against high-protein diets
- American Heart Association paper on high-protein diets in Circulation
- American Dietetic Association statement about low-carb diets