Was Atkins Right? Most Effective Weight Loss Diet Revealed
Scientists at Aberdeen’s Rowett Research Institute have shown that a high protein, low carbohydrate diet is most effective at reducing hunger and promoting weight loss, at least in the short term.
Healthy, obese men were given two different diets during their stay in the Rowett’s specialised Human Nutrition Unit. Both diets had a high protein content (30% of total energy value of the diet) but they differed in the amount of carbohydrate: One diet was low in carbohydrate (4%) and the other contained a moderate amount of carbohydrate (35% total energy value).
“Our volunteers found both diets to be equally palatable, but they felt less hungry on the high-protein low-carbohydrate diet compared with the diet which contained high-protein but moderate amounts of carbohydrate,” said Dr Alex Johnstone, the Rowett’s weight-loss expert who led the study.
“Weight loss during the two four week study periods was greater on the high-protein low-carbohydrate diet, averaging 6.3 kg per person, compared with 4.3 kg on the moderate carbohydrate diet,” said Dr Johnstone.
An important part of this study was to unravel the physiological mechanisms behind this type of diet. It is known that when people eat low carbohydrate diets, within a relatively short time their body has to switch from using glucose as a fuel to using something different called ketone bodies. Ketone bodies are appetite-suppressing and they may have an effect on the appetite centres in the brain. It’s also well known that protein itself is very good at making people feel full-up.
“In this study, we showed that on the high-protein low-carbohydrate diet the volunteers became ketogenic within 1-2 days of starting this diet and so it may be that high-protein, low-carbohydrate diets are particularly effective because of the combined effect of the protein and the ketone bodies,” said Dr Johnstone.
“We showed that the volunteers on the ketogenic diet reduced their energy intake without increasing their hunger and this was a very important factor in their ability to stick to the diet.”
Dr Johnstone sounds a note of caution about her findings: “A paper published last year from the same study showed that low carbohydrate diets may have consequences for the health of the gut by dramatically reducing the numbers of particular types of bacteria. So we will be looking in more detail at the complex way in which we respond to changes in our diet before we can say whether low-carbohydrate ketogenic diets are a suitable tool for everyone who wants to lose weight.”
When the phase of the study which involved the volunteers finished in October 2004, it attracted considerable interest because of its celebrity volunteer, Cameron Stout, who lost just over 12 kg during his nine week stay at the Rowett Institute. At the time, Cameron mentioned his surprise at not feeling hungry during the study and said he had adjusted to eating smaller portions.
Am J Clin Nutr. 2008 Jan;87(1):44-55.
Effects of a high-protein ketogenic diet on hunger, appetite, and weight loss in obese men feeding ad libitum.
Johnstone AM, Horgan GW, Murison SD, Bremner DM, Lobley GE.
Division of Obesity and Metabolic Health and Biomathematics and Statistics Scotland, Rowett Research Institute, Aberdeen, United Kingdom.
BACKGROUND: Altering the macronutrient composition of the diet influences hunger and satiety. Studies have compared high- and low-protein diets, but there are few data on carbohydrate content and ketosis on motivation to eat and ad libitum intake. OBJECTIVE: We aimed to compare the hunger, appetite, and weight-loss responses to a high-protein, low-carbohydrate [(LC) ketogenic] and those to a high-protein, medium-carbohydrate [(MC) nonketogenic] diet in obese men feeding ad libitum. DESIGN: Seventeen obese men were studied in a residential trial; food was provided daily. Subjects were offered 2 high-protein (30% of energy) ad libitum diets, each for a 4-wk period-an LC (4% carbohydrate) ketogenic diet and an MC (35% carbohydrate) diet-randomized in a crossover design. Body weight was measured daily, and ketosis was monitored by analysis of plasma and urine samples. Hunger was assessed by using a computerized visual analogue system. RESULTS: Ad libitum energy intakes were lower with the LC diet than with the MC diet [P = 0.02; SE of the difference (SED): 0.27] at 7.25 and 7.95 MJ/d, respectively. Over the 4-wk period, hunger was significantly lower (P = 0.014; SED: 1.76) and weight loss was significantly greater (P = 0.006; SED: 0.62) with the LC diet (6.34 kg) than with the MC diet (4.35 kg). The LC diet induced ketosis with mean 3-hydroxybutyrate concentrations of 1.52 mmol/L in plasma (P = 0.036 from baseline; SED: 0.62) and 2.99 mmol/L in urine (P < 0.001 from baseline; SED: 0.36). CONCLUSION: In the short term, high-protein, low-carbohydrate ketogenic diets reduce hunger and lower food intake significantly more than do high-protein, medium-carbohydrate nonketogenic diets.
(The study which investigated the impact of the low carbohydrate, high-protein diet on the bacteria in the gut was published in Applied and Environmental Microbiology, 73:1073-8.)