Sarah Di Lorenzo: How to balance rapid weight loss on the Keto diet with long-term nutritional needs

Most of us have heard about ketosis. For so many it can be an effective way to lose body fat and, once adapted, can support steadier energy and mental clarity. But the experience of being in a ketogenic state and ketosis varies for individuals.

But first, ketosis is a metabolic state where your body uses fat and ketones as its main fuel instead of glucose.

Ketosis is a powerful tool for weight loss when done properly and strategically and best following a program or under the guidance of a clinical nutritionist or dietician. This is achieved by removing complex carbohydrates from the diet and eating specific fruit and vegetables that are low carb and high fibre.

The first stages of going into ketosis can be unpleasant with many people experiencing “the keto flu”. This happens in the early stages and does pass, but you need to persevere — the results are worth it.

Ketosis is not inherently dangerous. I don’t recommend being in ketosis long term (by that I mean years). Staying in deep ketosis continuously for very long periods is not necessary for most people’s long-term health or weight maintenance. You can go in and out of ketosis during your weight loss journey.

I recommend breaks for a few reasons, one is having people understand that long term that healthy eating involves carbohydrates and I have found people in ketosis for long periods can develop a fear of carbs which can take time to unravel.

So how long is too long in ketosis? Ketosis, where blood ketones are around 0.5–3.0 mmol/L, is achieved by restricting carbohydrates to roughly 20–50g per day, depending on the person. You can be in mild ketosis around 70g or carbs per day. Again, this depends on the individual.

Clinical and research guidelines suggest that a carefully curated ketogenic diet can be followed from a few weeks to about six months under appropriate supervision.

For example, a 24-week trial in people with obesity using a ketogenic diet found significant weight loss and improvements in triglycerides, LDL, HDL and blood glucose, without major adverse effects over that period.

I recommend to all my weight loss patients to have a break around the six month mark with a slow transition from ketosis to introducing carbohydrates slowly back into the diet.

While being in strict ketosis gets results, there are factors that you need to consider and be aware of. In some cases there can be nutrient gaps if not enough vegetables, fibre and micronutrient-dense foods are included. There are possible impacts on gut microbiota diversity when fibre sources are overly restricted.

In practice, the “too long” question varies by individual. It can depend on your medical status, how well the diet is put together and how you are being managed throughout. Most guidance points to using ketogenic phases as a tool and counting in months rather than continuous ketosis for years.

As a weight loss specialist clinical nutritionist, I primarily use ketosis for weight loss. It really is effective for many reasons. Ketosis helps regulate our appetite regulation and calorie intake. Ketone bodies have appetite-suppressing effects, and very-low-carb, higher-protein diets increase satiety hormones such as GLP-1 and cholecystokinin.

People on very-low-carb ketogenic diets often eat fewer calories spontaneously yet report less hunger than those on low-fat diets, as well lower insulin and increased fat burning. When you restrict carbohydrate intake markedly lowers post-prandial (after meal) glucose and insulin levels.

With insulin low and glucagon relatively higher, the body breaks down stored fat, increases lipolysis and produces ketones. This means fat as a primary fuel and can enhance loss of adipose tissue over time. It also means improved metabolic health, especially for those who are insulin resistant.

Research shows ketogenic diets can be really effective in people with obesity and type 2 diabetes, improving glycaemic control, insulin sensitivity, triglycerides and HDL cholesterol. Plus better insulin sensitivity and more stable blood glucose makes it easier to control cravings, especially sugar cravings and avoid energy crashes supporting the weight loss journey.

Another pro is the food consumed includes good fats, proteins and whole foods, removing all processed and ultra processed foods.

The downside to be aware of when using ketosis for weight management is that while ketosis is effective for losing weight, long term maintenance is more about sustainability than staying in a strict metabolic state forever.

Those without guidance can regain weight after stopping keto if they return to previous eating patterns or reintroduce large amounts of refined carbohydrate without adjusting portions. Plus very restrictive versions of keto can be socially and psychologically hard to maintain.

When my patients have reached their goal weight from being in ketosis, I tell them the old eating style is abnormal as it leads to disease (such as obesity, T2D and IR) and they need to learn a new style of eating. The low carb keto diet is the foundation of a new eating plan with a slow introduction of carbohydrates and only ever at breakfast and or lunch.

Being in ketosis is an effective weight loss tool. You feel amazing in a ketogenic state, it preserves muscle which is so important as muscle is active tissue and helps regulate blood glucose and our metabolic rate.

Ketosis under guidance is an amazing weight loss tool and also a good tool to lower any chronic disease. Follow a program properly, have breaks at the six-month mark and when you are at your goal, establish an eating plan that is to be your new normal.