Error editing ViewModel data

In design I have a ViewModel and inside it my models and everything. What happens is that I'm trying to edit data that is already saved in the database.

I can bring the edited data of the view, but when I actually save it, this error is generated:

  

An exception of type 'System.Data.Entity.Infrastructure.DbUpdateConcurrencyException' occurred in EntityFramework.dll but was not handled in user code

     

Additional information: Store update, insert, or delete statement (0). Entities may have been modified or deleted since classes were loaded. See link for information on understanding and handling optimistic concurrency exceptions.

I do not know what I might be doing wrong when editing and saving these data ...

Well, the POST action that does the editing of this data, has the following code:

         [HttpPost]
    public ActionResult Edit(AnamineseViewModel anamneseViewModel)
    {
        if (ModelState.IsValid)
        {
            AnaAnamineseAlimentar anamnese = db.AnaAnamineseAlimentar.Find(anamneseViewModel.AnaAnamineseAlimentar.AnaId);
            CliCliente cliente = db.CliCliente.Find(anamneseViewModel.CliCliente.CliId);
            RecRecordatorio recordatorio = db.RecRecordatorio.Find(anamneseViewModel.RecRecordatorio.AnaId);
            List<RefRefeicao> refeicao = anamneseViewModel.RefRefeicao;
            List<QfaQuestionarioFrequenciaAlimentar> qfa = anamneseViewModel.QfaQuestionarioFrequenciaAlimentar;

            cliente = anamneseViewModel.CliCliente;
            anamnese = anamneseViewModel.AnaAnamineseAlimentar;
            recordatorio = anamneseViewModel.RecRecordatorio;
            refeicao = anamneseViewModel.RefRefeicao;
            qfa = anamneseViewModel.QfaQuestionarioFrequenciaAlimentar;

            var cliCliente = db.Set<CliCliente>().Local.FirstOrDefault(f => f.CliId == anamneseViewModel.CliCliente.CliId);

            if (cliCliente != null)
            {
                db.Entry(cliCliente).State = EntityState.Detached;
            }

            db.Entry(cliente).State = EntityState.Modified;

            var anaAnamnese = db.Set<AnaAnamineseAlimentar>().Local.FirstOrDefault(f => f.AnaId == anamneseViewModel.AnaAnamineseAlimentar.AnaId);

            if (anaAnamnese != null)
            {
                db.Entry(anaAnamnese).State = EntityState.Detached;
            }

            db.Entry(anamnese).State = EntityState.Modified;

            var recrecordatorio = db.Set<RecRecordatorio>().Local.FirstOrDefault(f => f.AnaId == anamneseViewModel.RecRecordatorio.AnaId);

            if (recrecordatorio != null)
            {
                db.Entry(recrecordatorio).State = EntityState.Detached;
            }

            db.Entry(recordatorio).State = EntityState.Modified;

            for (int i = 0; i < refeicao.Count; i++)
            {
                var refRefeicao = db.Set<RefRefeicao>().Local.FirstOrDefault(f => f.RefId == anamneseViewModel.RefRefeicao[i].RefId);

                if (refRefeicao != null)
                {
                    db.Entry(refRefeicao).State = EntityState.Detached;
                }

                db.Entry(refeicao[i]).State = EntityState.Modified;
            }

            for (int i = 0; i < qfa.Count; i++)
            {
                var qfaQfa = db.Set<QfaQuestionarioFrequenciaAlimentar>().Local.FirstOrDefault(f => f.QfaId == anamneseViewModel.QfaQuestionarioFrequenciaAlimentar[i].QfaId);

                if (qfaQfa != null)
                {
                    db.Entry(qfaQfa).State = EntityState.Detached;
                }

                db.Entry(qfa[i]).State = EntityState.Modified;
            }

            db.SaveChanges();
            return RedirectToAction("Index");
        }

        return View(anamneseViewModel);
    }

I can return the data, but in db.SaveChanges() the error is generated .. How could I solve it?